Effect of the active cooling and dwell time to tensile properties of AZ31 wall components by wire-arc directed energy deposition

Effect of the active cooling and dwell time to tensile properties of AZ31 wall components by wire-arc directed energy deposition | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of the active cooling and dwell time to tensile properties of AZ31 wall components by wire-arc directed energy deposition Hideaki Nagamatsu, Hiroyuki Sasahara This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7770019/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Apr, 2026 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract Wire-arc directed energy deposition (DED) has been a promising additive manufacturing technology for safety and rapidly fabricating magnesium (Mg) alloy components. However, high heat input from the electric arc can degrade geometric accuracy and cause grain coarsening. This is a critical issue for Mg alloys because their mechanical properties are strongly influenced by grain size. One common solution is to pause the deposition process until the component cools to an appropriate temperature, which significantly reduces the manufacturing rate. To address this issue, our study proposes a novel active cooling method for the Mg alloy deposition process: solid-contact active cooling (SCAC). This method involves direct contact between copper blocks and the fabricated component. We fabricated AZ31 alloy walled components using three cooling methods: no active cooling (NAC), SCAC with copper blocks (SCAC-C), and SCAC with internal water circulation (SCAC-W). The manufacturing rate reached up to 364 cm³/h. NAC with a short interpass dwell time resulted in frequent weld sagging, coarser grains, and decreased tensile properties. In contrast, SCAC-C with a short interpass dwell time led to finer grains and improved surface quality, even though the copper blocks reached 500℃. The SCAC-W was the most effective, as the water-cooled copper blocks remained below 50℃, resulting in the finest grains and the best tensile properties. These results demonstrate that the SCAC method, particularly the SCAC-W, can prevent grain coarsening and degradation of tensile properties while achieving a significantly higher manufacturing rate. additive manufacturing magnesium alloy active cooling dwell time microstructure tensile properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Magnesium (Mg) alloys are the lightest and have the highest specific strength among metals used in the manufacturing industry, sparking interest in developing products with additive manufacturing (AM) technologies [ 1 ]. Among metal AM processes, wire-arc directed energy deposition (DED) is a suitable method for the three-dimensionally fabricating Mg alloys [ 2 ]. Wire-arc DED uses Mg alloy wire as the filler, avoiding the risks associated with Mg alloy powders, such as flammability and explosiveness. Wire-arc DED is also more energy efficient than laser-based AM [ 3 ]. Consequently, there is a global effort to develop Mg alloy products using TIG [ 4 , 5 ] and MIG [ 6 , 7 ] based wire-arc DED, primarily in the United States and China [ 1 ]. Many fusion-based metal DED processes, including wire-arc DED, input high thermal energy into the fabricated components, causing them to become excessively hot. In metal AM, excessive heating can lead to issues such as a loss of geometrical accuracy due to weld sagging [ 8 ] and a decrease in mechanical properties caused by grain coarsening and the precipitation of intermetallic compounds [ 9 ]. While common countermeasures include reducing the material feed rate [ 10 ] or introducing dwell times between layers, these methods unfortunately lower the manufacturing rate [ 8 ]. Active cooling methods have gained attention as a way to improve the mechanical properties and manufacturing rate of the fabricated components. Studies on water bath cooling—the most effective active cooling method for metal AM processes—have demonstrated advantages such as grain refinement, reduced grain size variation, and anisotropy in mechanical properties for Inconel 718 [ 11 ]. Additionally, it has been shown to enable the high-speed fabrication of duplex stainless steel while maintaining quality [ 12 ]. Furthermore, the mechanical properties of hexagonal close-packed Mg alloys depend more on grain size compared to other materials [ 13 , 14 ]. Improvements in both strength and ductility are expected from grain refinement and the suppression of twin deformation [ 15 ]. Thus, developing an active cooling method suitable for Mg alloy AM technology could improve the manufacturing rate and enhance both strength and ductility through grain refinement. However, water bath cooling is unsuitable for Mg alloy AM due to the risk of a combustion reaction between high-temperature Mg and water, and the formation of pores caused by a drastic decrease in hydrogen solubility during solidification [ 4 ]. Therefore, we focused on a solid contact-based active cooling (SCAC) system that directly contacts a solid cooling medium with the molten metal. SCAC uses materials with high thermal conductivity such as pure copper or devices with high heat dissipation efficiency as the cooling medium. Zhang et al. improved the strength, grain refinement, and reduced the porosity of Al-Si alloy fabricated walls by SCAC employing a pure copper plate [ 16 ]. Li et al. improved the manufacturing rate and surface quality of 2325 Al alloy fabricated walls using thermoelectric cooling technology [ 17 ]. Additionally, Ma et al. used a water-cooling plate (material unspecified) to improve the cooling rate, grain refinement, and strength and ductility of AZ31 fabricated walls [ 18 ]. In our previous study, AZ31 walls were fabricated by no active cooling (NAC), an SCAC with a pure copper block (SCAC-C), and an SCAC with a copper block that had an internal water circulation mechanism (SCAC-W) [ 19 ]. We clarified how the placement of the copper blocks and the processing conditions affect arc deflection, droplet transfer, geometrical accuracy, and the temperature of the fabricated walls and the copper blocks. As described above, although there are very few research examples, SCAC has been reported to improve the manufacturing rate and mechanical properties of fabricated components. It is expected to be an effective active cooling technique for active metals such as aluminum (Al) and titanium (Ti) alloys, that are not suitable for direct water cooling. SCAC can also help avoid hydrogen embrittlement—a risk associated with direct water cooling. Currently, SCAC is only used for fabricating wall structures; however, it could create free-form shapes by developing a roller-based cooling medium instead of a plate. Xie et al. fabricated a meter-sized turbine blade-like structure by rolling the sides of the bead with two rollers, though not for the purpose of active cooling [ 20 ]. To demonstrate the effectiveness of SCAC, it is particularly important to achieve a high manufacturing rate of DED-fabricated components while maintaining their quality. However, to the best of our knowledge, the impacts of actively increasing the manufacturing rate (reducing the dwell time between layers) on the mechanical properties of the components have not yet been clarified. For instance, Zhao et al. have continuously fabricated a large-scale shell-shaped Al-Si alloy component with a total of 753 layers and high geometric accuracy by optimizing the process parameters without active cooling [ 21 ]. Although not explicitly stated in the paper, the manufacturing rate is estimated to be 317 cm³/h. In contrast, the manufacturing rates in all prior SCAC studies are below 300 cm³/h as shown in Table 1 . Therefore, this study investigates the effects of reducing the dwell time between layers and SCAC on the tensile properties of the AZ31 wall. The maximum manufacturing rate adopted in this study is 364 cm³/h. To examine the cooling rate of the AZ31 walls, we measured the temperature history, the geometric accuracy, and the grain size of the fabricated wall or the cooling media used. Additionally, we discussed the potential of SCAC to further increase the manufacturing rate of the wire-arc DED. Table 1 Comparisons among the manufacturing rates of wire-arc DED components with and without active cooling methods. Process Material Manufacturing rate Wire diameter Wire feed speed WFS Travel speed TS Dwell time Bead length Annotation and references [cm 3 /h] [mm] [m/min] [mm/min] [s] [mm] Natural cooling ER4043 317 1.2d 4.67 618 0 ? WFS and TS were the average values calculated from Table 5 of the cited paper [ 21 ]. Active cooling WE43 271 1.2 8.0 600 30 300 [ 22 ] Active cooling AZ31 229 1.2 6.2 450 70? 100? The bead length was estimated from the substrate dimensions (120 mm). The dwell time was estimated from Fig. 2 in the cited paper [ 18 ]. Active cooling 2325 Al alloy 88 1.2 4.0×2 300 78 100 Dwell time was calculated from the cooling time (2880 s) and number of layers (37 layers) specified in Table 3 of the cited paper [ 17 ]. 2. Experimental methods 2.1 Material used Table 2 presents the nominal chemical compositions of the wire and the substrate used equivalent to the AZ31-Mg alloy. The wire has a diameter of 1.2mm, and the dimensions of the substrate are 150 × 40 × 5 mm. Table 3 shows the physical properties of the copper blocks used as the cooling medium. The copper blocks are equivalent to the JIS standard C1100P. Table 2. Nominal chemical composition of the wire and the substrate used (wt.%). Al Zn Mn Si Fe Cu Ni Mg 2.5 0.7 0.2 0.30 0.005 0.05 0.005 Bal. Table 3. Physical properties of the copper blocks used as the cooling medium equivalent to the JIS standard C1100P. Properties Unit Value Specific heat [-] 385 Coefficient of expansion [10 −6 ·K] 17.7 Thermal conductivity [W/(m·K)] 391 Electroconductivity [%IACS] ≥ 97 Liquidus temperature [°C] 1083 Solidus temperature [°C] 1065 2.2 Fabrication process The welding power source was a MIG welder (WB-P500L, DAIHEN Corp.). The wire-arc DED system consists of three orthogonal axes and CNC device that controls the trajectory of the welding torch (BTA300-30, DAIHEN Corp.), which is attached to the Z-axis plate. Fig. 1 shows a schematic diagram of the active cooling system. An Mg alloy straight bead was deposited in the gap between two parallel copper blocks (Fig. 1(a)). During the arc-off period, the copper blocks were raised to match the layer height, maintaining contact between the molten Mg and the copper blocks. Repeating these steps fabricated a wall component with a height of approximately 60 mm, a length of approximately 100 mm (with 80 mm path length), and a width of approximately 14 mm. Note that the molten Mg did not bond to the copper blocks in all deposition processes. The copper blocks used for SCAC-C were shaped 200 × 15 × 15 mm in size (Fig. 1(b)). The copper blocks used for SCAC-W were 200 × 22 × 22 mm with a central long hole of Φ14.5 mm (Fig. 1(c)). Water tube adapters and hoses connected the blocks to an external water tank. An electric pump circulated cooling water at approximately 12°C inside the blocks. The volumetric flow rate of the cooling water was 3×10 −4 m³/s, and the flow velocity was 1.9 m/s. Table 4 shows the common processing parameters. The welding mode was a direct current pulse. Compared to other AM fabrication examples, a very high material feed rate of 774 cm 3 /h was used. Argon gas with a concentration of at least 99.9% was used as shielding gas. Table 5 shows the individual processing parameters. The interpass dwell time ( t ) for each layer was either 60 s or less or 120 s or more. The manufacturing rate with t =18 s is 364 cm 3 /h. The abbreviations defined in this paper—NAC, SCAC-C, and SCAC-W—are synonymous with FCC (free convection cooling), SCAC, and SCACW, respectively, as described in our previous study [19]. Table 4. Common processing parameters. Parameters Unit Value Average output current [A] 106 Wire feed speed [mm/min] 11.4 Deposition rate [cm 3 /h] 774 Travel speed [mm/min] 300 Welding torch to work distance [mm] 12.5 Path length along X axis [mm] 80 Flow rate of shielding Ar gas [L/min] 25 Table 5. Individual processing parameters. Test No. Cooling method W Average output voltage U Dwell time per layer t Manufacturing rate [mm] [V] [s] [cm 3 /h] 1 NAC (No active cooling) - 18.1 42 213 2 NAC - 18.1 126 87 3 NAC - 22.4 42 213 4 NAC - 22.4 150 75 5 SCAC-C 14 22.4 18 364 6 SCAC-C 14 22.4 132 84 7 SCAC-W 14 22.4 18 364 8 SCAC-W 14 22.4 126 87 2.3 Measurement of grain size and tensile properties Fig. 2 illustrates the method used to evaluate the grain size and the geometry of the tensile test specimen. Fig. 2(a) shows an actual image of the fabricated wall and the sampling location for microstructure observation. The central portion of the fabricated wall was cut using electrical discharge machining (EDM). The cross-section of the resin-embedded specimen in the Y-Z plane was polished using SiC abrasive paper with #1000 and #2000 grit, as well as diamond suspensions with 6 µm and 1 µm particle sizes. The polished surface of the specimen was then etched for approximately 20 seconds in a room-temperature solution containing 5 g of picric acid, 5 mL of acetic acid, 10 mL of purified water, and 100 mL of ethanol to reveal the grain boundaries (Fig. 2(b, c)). The grain size measurement area was the center of the wall in the Y-Z plane (-0.5 mm < Y < 0.5 mm). Grain size in the height direction was evaluated by determining the intersections of three 10-mm-long test lines crossing the heat-affected zone (HAZ) and fusion zone with the grain boundaries (Fig. 2(c)) using a digital microscope (VHX-6000, Keyence Corp.). The tensile test specimens were cut from the center of the fabricated wall using EDM such that the tensile direction was parallel to the build height. The geometry of the tensile test specimen is shown in Fig. 2(d). The length, width, and thickness of the parallel section were 30.1 mm, 5 mm, and 3.1 mm, respectively. Tensile tests were performed at room temperature using a universal testing machine (Z100 THW 100kN, Zwick Roell Corp.). The representative value for each condition was taken as the average value of more than six test results where fracture occurred in the parallel section. 3. Results and discussion 3.1 Temperature of copper block and wall components Fig. 3 illustrates the temperature measurements of the copper block during arc discharge using a thermal camera (T630sc, Teledyne FLIR LLC). The temperature history shows the average temperature at the center of the copper block’s surface. The block was pre-coated with a black body spray (emissivity 0.94) as shown in Fig. 3(a). Figs. 3(c, d, e) show the average temperature histories of the copper blocks for Nos. 6 (SCAC-C, t = 132 s), 5 (SCAC-C, t = 18 s), and 7 (SCAC-W, t = 18 s), respectively. As shown in Fig. 3(c), it is evident that the copper block temperature increased with the number of layers under the SCAC-C with a relatively long t . However, the temperature history from the 11 th layer onwards was generally consistent. This is because a balance was established between the heat input from the arc discharge and the increased heat dissipation from the sidewall with each additional layer. With a short t (No. 5, Fig. 3(d)), the temperature of the copper block was significantly higher than that of No. 6. Comparing the temperature histories of the 12 th and 18 th layers reveals that the interpass temperature of the copper block immediately prior to arcing increased from approximately 410°C to 500°C, while the maximum temperature increased from approximately 500°C to 570°C. In contrast, for the SCAC-W with a short t (No. 7, Fig. 3(e)), the copper block temperature only increased by approximately 10°C even as the number of layers increased. Fig 3(b) shows the transition of the maximum temperature of the copper block for each layer. The average maximum temperatures from the 12 th to 14 th layers for Nos. 5, 6, 7, and 8 were 518°C, 232°C, 22°C, and 32°C, respectively. These results demonstrate that the SCAC-W can largely maintain its initial temperature even with a dwell time of only 18 seconds. Fig. 4 shows the temperature measurement of the fabricated wall during the arc-off period. The emissivity of the AZ31 fabricated wall is difficult to identify because MIG welding of AZ31 generates a lot of black powder called smut. Therefore, instead of using a non-contact temperature sensor, the temperature of the top layer of the wall was measured with a K-type thermocouple (TH-8292-2, THREE HIGH CO.,LTD.) in direct contact with the wall (Fig. 4(a)). The measured walls were Nos. 4 (NAC, t = 150 s), 6 (SCAC-C, t = 132 s), and 8 (SCAC-W, t = 126 s). Their processing conditions were identical except for their cooling method and their interpass dwell time was relatively long. Fig. 4(b) shows the temperature history of the top layer after the 10 th layer was deposited. 100 seconds after arc-off, the temperatures for Nos. 4, 6, and 8 were 129°C, 168°C, and 97°C, respectively. No. 6 (SCAC-C) had the highest temperature. This is due to the contact heat transfer from the copper blocks, which was heated to over 150°C. However, the cooling rate of No. 6 during arc-on may be higher than that of No. 4 (NAC) because the temperature of No. 6 was lower than that of NAC 30 seconds after arc-off. As shown in Fig.4 (b), the cooling rates for Nos. 6 and 8 (SCAC-W) were 0.91°C/s and 1.25°C/s, respectively, 60 seconds after arc-off. Fig. 4(c) shows the temperature measurement for each layer 40 seconds after arc-off. The average temperatures from 10 th to 12 th layers for Nos. 4, 6, and 8 were 209°C, 196°C, and 148°C, respectively. From the above, we clarified that SCAC-W can effectively lower the temperature of the copper block and the fabricated wall. To understand the effects of the active cooling method on the microstructure, it is essential to measure the temperature data near the molten pool during arc-on, including maximum temperature, holding time, and cooling rate above recrystallization temperature. Section 3.3 will discuss the cooling rate for the fabricated walls with a short interpass dwell time, such as Nos. 5 and 7, based on the grain size observation results. 3.2 Surface quality Fig. 5 illustrates the scan data of all the fabricated walls, which were acquired using a 3D coordinate measuring machine (VL300, Keyence Corp.). The color maps indicate the difference between the average Y-coordinate within the inspection range and the point cloud for each side surface of the wall. Deep concavities with a difference of -1 mm or less are shown in blue, while large convexities with a difference of 1 mm or more are shown in red. The side surface roughness of the wall was evaluated by the arithmetic mean height (Sa), which is calculated using the following equation: As shown in the NAC walls (Fig. 5(a-d)), weld sagging frequently occurred and surface roughness increased with an increase in welding voltage and a decrease in interpass dwell time. In particular, for No. 3 (NAC, 22.4 V, t = 42 s), the molten pool became oversized and flowed in the width direction (Y-axis), making further deposition difficult. Therefore, deposition was stopped at the 12 th layer. These results highlight the importance of setting appropriate heat input conditions, such as an interpass dwell time to achieve a near-net shape through natural cooling. For the SCAC-C walls (Fig. 5(e, f)), the surface roughness decreased to 0.09 mm as the interpass dwell time decreased. Continuous heat input raised the temperature around the molten pool. This resulted in the molten metal with low surface tension spreading over the entire space between the copper blocks. A similar trend was observed for the SCAC-W walls (Fig. 5(g, h), though the overall surface roughness was lower than that of the SCAC-C walls. This is due to increased kinematic viscosity and decreased wettability of the molten metal, which were caused by higher cooling rate and lower temperature of the fabricated walls. These results do not indicate a decrease in geometrical accuracy for SCAC-W; rather, they show that the fabricated wall can be sufficiently cooled with a short interpass dwell time. Therefore, SCAC-W has the potential to be applied to a wire-arc DED process with an even shorter interpass dwell time ( t < 18 s). In contrast, the copper block temperature can increase further for SCAC-C, which may cause the cooling rate of the fabricated wall to drop below that of NAC. 3.3 Microstructure Fig. 6 shows the microstructure images and grain size distribution maps for Nos. 3, 4, 5, and 7, all with a welding voltage of 22.4V. A sufficiently wide inspection area was evaluated, with approximately 300 to 900 grains examined. As the microstructure images in Figs. 6(c, e, g) show, the grains in the HAZ are coarser than those in the fusion zone, regardless of the cooling method. The grains in No. 3 (NAC, t = 42 s), where significant weld sagging occurred, were the largest among all processing conditions (Figs. 6(a, b)). The average grain size was 148 µm and the grains larger than 280 µm accounted for 7% of the total. Please note that the boundary between the HAZ and the fusion zone was unclear; therefore, the boundary line is not indicated in the image. In No. 4 (NAC, t = 150 s), the grains were more refined than in No. 3. The average grain size was 67 µm and no grains larger than 280 µm were observed in the inspection area (Figs. 6(c, d)). In Nos. 5 (SCAC-C, t = 18 s) and 7 (SCAC-W, t = 18 s), grain refinement was observed throughout the entire inspection area, despite the significantly shorter interpass dwell time compared to No. 4. The average grain size of No. 5 was 58 µm. This result suggests that the contact heat transfer from the copper block, which was heated to an interpass temperature of 500°C (Fig. 3(d)), provided the fabricated wall with a higher cooling rate than the heat transfer from the NAC wall to the atmosphere. The average grain size of No. 7 was 43 µm, which was the smallest among the four conditions shown in Fig. 6. It is believed that the cooling rate of the fabricated wall improved due to heat transfer from the water-cooled copper block which remained below 50°C. The change in grain size in the width direction (Y-axis) was measured. Fig. 7 shows the macro- and microstructures in the HAZ of No. 7 (SCAC-W, t = 0.3 min). Magnified microstructure images of regions b and c in Fig. 7(a) are shown in Figs. 7(b, c), respectively. Similarly, magnified images of regions d and e in Fig. 7(c) are shown in Figs. 7(d, e), respectively. The observation images shown in Figs. 7(d, e) are approximately 550 µm × 730 µm in size. To evaluate the aspect ratio, three test lines were drawn in both the width and height directions (Y- and Z-axes). The grain size measurement results along the width direction are shown in Fig. 7(f). The average grain size at the center of the fabricated wall was 80 µm, with an aspect ratio of approximately 1.2 (ratio of grain size in the height direction relative to the width direction). This indicates that the grains grew slightly in the build height direction (Fig. 7(e)). Since the heat transfer direction inside a wire-arc DED-fabricated component is predominantly in the height direction, the grains in the central part tend to grow in that direction. In contrast, the average grain size near the side surface was 47 µm with an aspect ratio of approximately 1.0. The grains refined into an equiaxed shape along the width direction as shown in Figs. 7(d, f). A characteristic columnar structure was also observed near the side surface (Fig. 7(b)). This occurred because a high-temperature gradient was generated at the interface where the copper block met the molten metal. This gradient caused the grains to grow toward the copper block. However, this structure was only observed within a limited region (300 µm) near the side surface where a relatively large, flat surface formed. The columnar structure was not observed under other conditions. Even in No. 8, most of the microstructure near the side surface was equiaxed, as shown in Fig. 7(d). 3.4 Tensile test Fig. 8 presents the results of the tensile tests. The bar graphs illustrate the average values, and the error bars indicate the standard deviation. For NAC, ultimate tensile strength (UTS), 0.2% yield strength (YS), and elongation (EL) all decreased as the interpass dwell time shortened. In contrast, a significant reduction in interpass dwell time (from 132 s to 18 s) caused a 2-3% decrease in EL for SCAC-C and SCAC-W, but had no significant effect on UTS or YS. Comparing conditions with relatively similar interpass dwell times ( t 120 s) reveals that both strength and ductility improved in the order of SCAC-W > SCAC-C > NAC. This trend aligns with previous studies reporting improvements in tensile properties due to grain refinement [13, 22–24]. Although the mechanical properties of magnesium alloys depend strongly on grain size, other factors―texture, microscopic orientation factors, and the morphology of eutectic compounds―can also influence them. Kamado et al. [9] reported that the tensile strength and ductility of the as-cast MC2 magnesium alloy were enhanced by both a reduction in the volume fraction of eutectic compounds and a blocky precipitation of these compounds near the three-grain junctions of the cell boundaries. Similarly, Li et al. [18] found that the strength enhancement of an active-cooled AZ31 wall is due to grain refinement strengthening and precipitation strengthening from the formation of nano-sized particles. Furthermore, Yoshida et al. [25] reported that the ductility of AZ31 significantly improved after equal-channel angular extrusion. This improvement was attributed to the activation of cross-slip from the basal plane to non-basal planes, in addition to basal slip. Therefore, a comprehensive investigation into the effects of active cooling on microstructural factors and crystal orientation is essential for future research. In summary, we clarified that active cooling improves both the manufacturing rate and the mechanical properties. Due to the limitations of our experimental setup, the minimum interpass dwell time was 18 seconds. However, SCAC-W (No. 7, t = 18 s) were able to maintain the copper block temperature below 50℃. Additionally, the grains of the SCAC-C walls (No. 5, t = 18 s) were finer than those in NAC walls, even when the copper blocks were heated to an interpass temperature of 500°C. Therefore, we believe that SCAC-W can prevent grain coarsening and the degradation of mechanical properties even with significantly shorter interpass dwell times (higher manufacturing rates). 4. Conclusions In this study, AZ31-walled components were fabricated by wire-arc DED with and without solid contact-based active cooling (SCAC). The temperature histories, side surface geometries, and microstructures of the fabricated walls were comprehensively evaluated. Finally, we examined the effects of SCAC and a shortened interpass dwell time on cooling rate and the tensile properties of AZ31 walls. Here are main conclusions: For no active cooling (NAC), frequent weld sagging occurred, and the grain size became coarser with a shorter interpass dwell time from 150 s to 42 s. For SCAC using copper blocks (SCAC-C), the interpass temperature of the copper block increased to 500°C with a significant reduction in interpass dwell time (from 132 s to 18 s). However, the grains were finer than NAC with a long interpass dwell time. For SCAC with an internal water circulation (SCAC-W), the copper block temperature was consistently maintained below 50°C, even with a reduction in interpass dwell time (from 126 s to 18 s). The fabricated walls had the finest microstructure among all processing conditions, and a columnar structure was also observed in a localized region near the contact surface with the copper blocks. The ultimate strength, yield strength, and elongation of the fabricated walls increased in the following order: SCAC-W > SCAC-C > NAC. The measurement results of the copper block temperature in the SCAC-C and SCAC-W processes suggest that SCAC-W can prevent grain coarsening and the degradation of tensile properties even with significantly shorter interpass dwell times. Declarations Funding This work was supported by The Japan Welding Engineering Society and The Light Metal Educational Foundation. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions H. Nagamatsu: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, validation, visualization, writing—original draft, writing—re-view & editing. H. Sasahara: funding acquisition, investigation, project administration, resources, supervision, writing—re-view & editing Data availability The authors confirm that the data supporting the findings of this study are available within the article and/or its supplementary materials. Acknowledgments We would like to acknowledge Japan Fine Steel Co., Ltd. for supplying the AZ31 wire; Prof. T. Kuboki and Associate prof. S. Kajikawa for permission me to use the universal testing machine and J. Kinoshita for his help developing the cooling device. References Manjhi SK, Sekar P, Bontha S, Balan ASS (2024) Additive manufacturing of magnesium alloys: Characterization and post-processing. International Journal of Lightweight Materials and Manufacture 7:184–213. https://doi.org/10.1016/j.ijlmm.2023.06.004 Li Y, Yin S, Zhang G, et al (2024) A Review on Wire Arc Additive Manufacturing of Magnesium Alloys: Wire Preparation, Defects and Properties. Met Mater Int. https://doi.org/10.1007/s12540-024-01724-7 Asadi P, Kazemi-Choobi K, Elhami A (2012) Welding of Magnesium Alloys. In: New Features on Magnesium Alloys. IntechOpen Fang X, Yang J, Wang S, et al (2022) Additive manufacturing of high performance AZ31 magnesium alloy with full equiaxed grains: Microstructure, mechanical property, and electromechanical corrosion performance. Journal of Materials Processing Technology 300:117430. https://doi.org/10.1016/j.jmatprotec.2021.117430 Guo Y, Quan G, Jiang Y, et al (2021) Formability, microstructure evolution and mechanical properties of wire arc additively manufactured AZ80M magnesium alloy using gas tungsten arc welding. Journal of Magnesium and Alloys 9:192–201. https://doi.org/10.1016/j.jma.2020.01.003 Wang P, Zhang H, Zhu H, et al (2021) Wire-arc additive manufacturing of AZ31 magnesium alloy fabricated by cold metal transfer heat source: Processing, microstructure, and mechanical behavior. Journal of Materials Processing Technology 288:116895. https://doi.org/10.1016/j.jmatprotec.2020.116895 Cao Q, Zeng C, Cai X, et al (2023) High-strength Mg-10Gd-3Y-1Zn-0.5Zr alloy fabricated by wire-arc directed energy deposition: Phase transformation behavior and mechanical properties. Additive Manufacturing 76:103789. https://doi.org/10.1016/j.addma.2023.103789 Heinrich L, Feldhausen T, Saleeby K, et al (2023) Build plate conduction cooling for thermal management of wire arc additive manufactured components. Int J Adv Manuf Technol 124:1557–1567. https://doi.org/10.1007/s00170-022-10558-9 Kamado S, Tsukuda M, Tokutomi I, Hirose K (1987) Effect of solidification conditions on mechanical properties of unidirectionally solidified AZ91C alloy. Journal of Japan Institute of Light Metals 37:721–728. https://doi.org/10.2464/jilm.37.721 Wang X, Wang A, Li Y (2020) Study on the deposition accuracy of omni-directional GTAW-based additive manufacturing. Journal of Materials Processing Technology 282:116649. https://doi.org/10.1016/j.jmatprotec.2020.116649 Kumar P, Sharma SK, Raj Singh RK (2023) Effect of cooling media on bead geometry, microstructure, and mechanical properties of wire arc additive manufactured IN718 alloy. Adv Manuf. https://doi.org/10.1007/s40436-023-00457-x Jorge VL, Scotti FM, Teixeira FR, et al (2025) Application of near-immersion active cooling for thermal management in arc additive manufacturing of thin super duplex stainless steel walls. Int J Adv Manuf Technol 137:3025–3048. https://doi.org/10.1007/s00170-025-15355-8 Hauser FE, London PR, Dorn JE (1956) Fracture of Magnesium Alloys at Low Temperature. JOM 8:589–592. https://doi.org/10.1007/BF03377735 Chino Y, Mabuchi M (2001) Plastic-forming processes for magnesium alloys. Journal of Japan Institute of Light Metals 51:498–502. https://doi.org/10.2464/jilm.51.498 Lukac P, Trojanova Z (2011) INFLUENCE OF GRAIN SIZE ON DUCTILITY OF MAGNESIUM ALLOYS. Materials Engineering 18: Zhang A, Xing Y, Yang F, et al (2021) Development of a New Cold Metal Transfer Arc Additive Die Manufacturing Process. Advances in Materials Science and Engineering 2021:1–15. https://doi.org/10.1155/2021/9353820 Li F, Chen S, Shi J, et al (2018) Thermoelectric cooling-aided bead geometry regulation in wire and arc-based additive manufacturing of thin-walled structures. Applied Sciences (Switzerland) 8:207. https://doi.org/10.3390/app8020207 Ma P, Wang C, Jia H, et al (2025) Simultaneous enhancement in deposition efficiency and nano-scale precipitation of high-strength AZ31 Mg alloy via water cooling assisted wire-arc directed energy deposition. Thin-Walled Structures 206:112689. https://doi.org/10.1016/j.tws.2024.112689 Nagamatsu H, Sasahara H (2022) Improvement of Cooling Effect and Dimensional Accuracy of Wire and Arc Additive Manufactured Magnesium Alloy by Active-Cooling-Based Contacting Copper Blocks. Journal of Manufacturing and Materials Processing 6:27. https://doi.org/10.3390/jmmp6020027 Xie Y, Zhang H, Zhou F (2016) Improvement in Geometrical Accuracy and Mechanical Property for Arc-Based Additive Manufacturing Using Metamorphic Rolling Mechanism. Journal of Manufacturing Science and Engineering 138:111002. https://doi.org/10.1115/1.4032079 Zhao Y, Jia Y, Chen S, et al (2020) Process planning strategy for wire-arc additive manufacturing: Thermal behavior considerations. Additive Manufacturing 32:100935. https://doi.org/10.1016/j.addma.2019.100935 Li K, Li B, Zhu L, et al (2024) Optimizing microstructure and strength of CMT-wire arc additive manufactured WE43 Mg alloy through a novel active cooling technique. Thin-Walled Structures 205:112453. https://doi.org/10.1016/j.tws.2024.112453 Wei J, He C, Qie M, et al (2023) Achieving high performance of wire arc additive manufactured Mg–Y–Nd alloy assisted by interlayer friction stir processing. Journal of Materials Processing Technology 311:117809. https://doi.org/10.1016/j.jmatprotec.2022.117809 J. A. CHAPMAN, D. V. WILSON (1962) The room-Temperature Ductility of Fine-Grain Magnesium. JOURNAL OF THE INSTITUTE OF METALS 91:39–40 Kobayashi T, Koike J, Yoshida Y, et al (2003) Grain Size Dependence of Active Slip Systems in an AZ31 Magnesium Alloy. JJapan InstMetals 67:149–152. https://doi.org/10.2320/jinstmet1952.67.4_149 Cite Share Download PDF Status: Published Journal Publication published 01 Apr, 2026 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 19 Dec, 2025 Reviewers agreed at journal 13 Nov, 2025 Reviewers invited by journal 27 Oct, 2025 Editor assigned by journal 11 Oct, 2025 First submitted to journal 09 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7770019","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":535759717,"identity":"1ec6b30a-be3d-4c67-b229-04cc1805b5eb","order_by":0,"name":"Hideaki Nagamatsu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYBACAyQ24wNsori18DAwMBtgiBLSwiZBlMPMGXgPfvxSs03env+MWTVPhR0Df/sBhuICPFosG/iSpWWO3Tbskcgxu81zJplB4kwCg/EMfA47wGMgLcF2m7FHgsfsNm/bAQaGGwwMxjz4tRj/lvh3274H6LBi3n8HGOSJ0GIm+bHtdmIPQ44ZM2/DAQYDgloO85hZM/bdTu65kVYsOedYMo/hmcQG/H453mN888e327bt/Yc3fnhTYycnd/zwMWN8IcbADETIzgCyGduM8ekAAcYf6MY8JqRlFIyCUTAKRhQAAJxdRhzjLt/1AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-4702-0397","institution":"The University of Electro-Communications: Denki Tsushin Daigaku","correspondingAuthor":true,"prefix":"","firstName":"Hideaki","middleName":"","lastName":"Nagamatsu","suffix":""},{"id":535759718,"identity":"be63a64c-862c-4f81-b04d-3eda3b12f995","order_by":1,"name":"Hiroyuki Sasahara","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hiroyuki","middleName":"","lastName":"Sasahara","suffix":""}],"badges":[],"createdAt":"2025-10-03 04:06:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7770019/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7770019/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-026-17843-x","type":"published","date":"2026-04-01T15:58:11+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":95401776,"identity":"d30fcc1d-d866-40b4-b692-8b74bfdab040","added_by":"auto","created_at":"2025-11-07 16:16:12","extension":"xml","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":8690,"visible":true,"origin":"","legend":"","description":"","filename":"jamtJAMTD2505694.xml","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/78304ee0a903e311210dbc8e.xml"},{"id":95526975,"identity":"c07c95c6-f71e-48fa-ad86-d63491d506c4","added_by":"auto","created_at":"2025-11-10 10:08:57","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":932,"visible":true,"origin":"","legend":"","description":"","filename":"JAMTD2505694157939.go.xml","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/df8007adc693d91bea2268ee.xml"},{"id":95526557,"identity":"7d6963bd-5798-49a6-978c-a8ff8d7e7c4c","added_by":"auto","created_at":"2025-11-10 10:07:14","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":946,"visible":true,"origin":"","legend":"","description":"","filename":"JAMTD2505694Import.xml","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/f03c115f1031e5b48b2cf7e7.xml"},{"id":95401782,"identity":"965b1d52-8917-4ca6-bf7a-6719538f0e40","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"xml","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":94780,"visible":true,"origin":"","legend":"","description":"","filename":"JAMTD25056940enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/4e175e77ecf7ec443fd2f8cd.xml"},{"id":95527043,"identity":"47585547-d57b-419a-8017-bd55a327caf6","added_by":"auto","created_at":"2025-11-10 10:09:13","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":661468,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/e9747c0402624756307e52b7.png"},{"id":95401789,"identity":"f94f47f7-6179-4fd9-ab13-d687dda99b95","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":710486,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/a608a5db1bae4cbaeac07e71.png"},{"id":95526650,"identity":"6e957c17-2697-41c7-9fb9-15725b287bdd","added_by":"auto","created_at":"2025-11-10 10:07:31","extension":"emf","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":4853648,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.emf","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/a23961fa0743932f6efa1788.emf"},{"id":95401803,"identity":"e117a6e0-0413-468f-b04e-d611ea00e701","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"emf","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1604748,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.emf","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/e72548dc677c2291c0518cc3.emf"},{"id":95526555,"identity":"8c74947b-29c3-4a03-b090-53990d1961fb","added_by":"auto","created_at":"2025-11-10 10:07:14","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1041060,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/6d012db700268a6e88ec40d9.png"},{"id":95401787,"identity":"a946445c-ff8d-4428-9bc3-dc30eb1c3105","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":999122,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/cad0db3102fce9eea411a128.png"},{"id":95401790,"identity":"ddef4401-aa49-4080-b85a-e8c1eef6fae0","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":780100,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/b3e88501bb0df9807e617262.png"},{"id":95527294,"identity":"5e9a8e8d-b3e8-4e8c-86b9-a825e168dad4","added_by":"auto","created_at":"2025-11-10 10:12:55","extension":"emf","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":155716,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.emf","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/1d534b0e9309a8c360d48682.emf"},{"id":95526756,"identity":"ea342795-0bc8-49f5-be6f-bb317de39050","added_by":"auto","created_at":"2025-11-10 10:07:48","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":98762,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/74f0e298cbfb87fd7f25a72d.png"},{"id":95527384,"identity":"f08f0ace-da1f-4960-b015-ad8c435bfd05","added_by":"auto","created_at":"2025-11-10 10:13:28","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":109707,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/3d43cc4cd6bdf864b31e4be8.png"},{"id":95526089,"identity":"a1f79f45-26d7-4478-845b-cc531ebe9bb0","added_by":"auto","created_at":"2025-11-10 10:06:14","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":271784,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/c42e76831af22ccb9b3e8ff7.png"},{"id":95401792,"identity":"16aa3e7d-8da4-489d-bfdf-e46abcaedc3f","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":171792,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/598e3012da904ccc029ea8b3.png"},{"id":95401798,"identity":"2102e29e-2e0b-445b-a0a5-5c2f406bac2c","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":146530,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/263002651be86e057e38d085.png"},{"id":95526182,"identity":"2e051c98-a4cd-417e-a9ae-4bcb9bea6d41","added_by":"auto","created_at":"2025-11-10 10:06:26","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":195538,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/1b340a23844e99e46e82b7f7.png"},{"id":95401796,"identity":"19d555ce-6b61-437a-9140-f46ed5c0333e","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":120902,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/ac8ae063ffa4db5e2c71d91b.png"},{"id":95526137,"identity":"2adf1b36-230f-4f7c-8812-3917b3c24df9","added_by":"auto","created_at":"2025-11-10 10:06:21","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":147802,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/52634830f4cc9cbf7051b5c1.png"},{"id":95401799,"identity":"52fb6878-1628-4b44-9729-a7b8be3f29ce","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"xml","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":95474,"visible":true,"origin":"","legend":"","description":"","filename":"JAMTD25056940structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/8e54e3c6ddc568db3d7329ad.xml"},{"id":95526470,"identity":"7df51605-ebe9-43fd-a2fa-1b60a58a6ce5","added_by":"auto","created_at":"2025-11-10 10:07:02","extension":"html","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":103120,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/e39fa61e7abfa4bdc0348351.html"},{"id":95401773,"identity":"8f1bc653-1e39-49d3-85d7-6f431867de75","added_by":"auto","created_at":"2025-11-07 16:16:12","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":657710,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of (a) the solid contact-based active cooling (SCAC) system, \u003cbr\u003e\n(b) the used copper blocks for SCAC-C, and (c) SCAC-W.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/191b35cfaac3ffd7b86ddb5d.png"},{"id":95401774,"identity":"91eadf5c-78e7-400d-990a-bc36cb79eada","added_by":"auto","created_at":"2025-11-07 16:16:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":708081,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental methods: (a) Fabricated component and sampling location for the microstructure observation; (b) Cross-sectional view of the component; (c) Grain size evaluation by the intercept method, (d) Schematic diagram of the tensile test sample.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/5e9bb32becee5014b7592b84.png"},{"id":95401778,"identity":"f947cac4-b267-4b44-a9ee-02149461921e","added_by":"auto","created_at":"2025-11-07 16:16:12","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2145457,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature of copper blocks during arc discharge measured by a thermal camera: (a) Schematic diagram for the measurement setup; (b) the maximum temperature of the copper block; (c, d, e) Average temperature history of copper block using processing condition Nos.6 (SCAC-C, \u003cem\u003et\u003c/em\u003e =132s), 5 (SCAC-C, \u003cem\u003et\u003c/em\u003e =18s), and 7 (SCAC-W, \u003cem\u003et\u003c/em\u003e=18s)\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/3a092538b297ccc535fa4a0e.png"},{"id":95526475,"identity":"8eb1ca4d-62e5-4e46-af43-b3b469efe986","added_by":"auto","created_at":"2025-11-10 10:07:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":505788,"visible":true,"origin":"","legend":"\u003cp\u003eInterpass temperatures of the top layer measured with a K-type thermocouple: (a) Schematic diagram for the measurement setup; (b) Interpass temperature histories of the 10\u003csup\u003eth\u003c/sup\u003e layer; (c) Interpass temperatures 40s during arc-off period. The measured walls were Nos. 4 (NAC, \u003cem\u003et\u003c/em\u003e = 150s), 6 (SCAC-C, \u003cem\u003et\u003c/em\u003e = 132s), and 8 (SCAC-W, \u003cem\u003et\u003c/em\u003e = 126s).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/d109af6c3bf745a87ed56634.png"},{"id":95401780,"identity":"c1ad61a3-f380-40d2-9c00-50ad1e2143fc","added_by":"auto","created_at":"2025-11-07 16:16:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1029783,"visible":true,"origin":"","legend":"\u003cp\u003eAppearance and scan data of all fabricated walls.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/d79f1b237750f11b8ba94879.png"},{"id":95525809,"identity":"5eca8b92-8ea9-4649-8669-61d1941df4c6","added_by":"auto","created_at":"2025-11-10 10:05:42","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":984975,"visible":true,"origin":"","legend":"\u003cp\u003e(a, c, e, g) Microstructure of the boundary between the heat affected zone (HAZ) and the fusion zone; (b, d, f, g) Grain size distribution maps.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/bd147ba9c4648b9213c4572a.png"},{"id":95526507,"identity":"aaa5ff9d-e132-4d52-ad91-8ff9b9ee087e","added_by":"auto","created_at":"2025-11-10 10:07:08","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":873476,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure images of No.8 (SCAC-W, \u003cem\u003et\u003c/em\u003e = 126 s); (a) Overview; (b) Columnar grains grown toward the copper contact surface in area b as shown in (a); (c) HAZ macrostructure in area c as shown in (a); (d) Equiaxed grains near the side in area d as shown in (c); (e) Microstructure at the center of the wall component in area e as shown in (c); (f) Average grain size along the width direction (Y-axis).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/8cc5489dec1f7a49bf65562a.png"},{"id":95401785,"identity":"55f7d17d-29a3-4ce9-9eb4-451bf0ef910a","added_by":"auto","created_at":"2025-11-07 16:16:13","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":390961,"visible":true,"origin":"","legend":"\u003cp\u003eTensile results of AZ31 fabricated walls along the build direction.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/c46acad6a218af00e05c8b60.png"},{"id":106343629,"identity":"900d3ad8-fdfd-4d00-8273-e1252a0cc3a8","added_by":"auto","created_at":"2026-04-07 16:07:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7386902,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7770019/v1/c62bef8f-8499-4812-ab8c-498259ab6bd2.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eEffect of the active cooling and dwell time to tensile properties of AZ31 wall components by wire-arc directed energy deposition\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMagnesium (Mg) alloys are the lightest and have the highest specific strength among metals used in the manufacturing industry, sparking interest in developing products with additive manufacturing (AM) technologies [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Among metal AM processes, wire-arc directed energy deposition (DED) is a suitable method for the three-dimensionally fabricating Mg alloys [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Wire-arc DED uses Mg alloy wire as the filler, avoiding the risks associated with Mg alloy powders, such as flammability and explosiveness. Wire-arc DED is also more energy efficient than laser-based AM [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Consequently, there is a global effort to develop Mg alloy products using TIG [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] and MIG [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] based wire-arc DED, primarily in the United States and China [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMany fusion-based metal DED processes, including wire-arc DED, input high thermal energy into the fabricated components, causing them to become excessively hot. In metal AM, excessive heating can lead to issues such as a loss of geometrical accuracy due to weld sagging [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] and a decrease in mechanical properties caused by grain coarsening and the precipitation of intermetallic compounds [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. While common countermeasures include reducing the material feed rate [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] or introducing dwell times between layers, these methods unfortunately lower the manufacturing rate [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eActive cooling methods have gained attention as a way to improve the mechanical properties and manufacturing rate of the fabricated components. Studies on water bath cooling\u0026mdash;the most effective active cooling method for metal AM processes\u0026mdash;have demonstrated advantages such as grain refinement, reduced grain size variation, and anisotropy in mechanical properties for Inconel 718 [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Additionally, it has been shown to enable the high-speed fabrication of duplex stainless steel while maintaining quality [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFurthermore, the mechanical properties of hexagonal close-packed Mg alloys depend more on grain size compared to other materials [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Improvements in both strength and ductility are expected from grain refinement and the suppression of twin deformation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Thus, developing an active cooling method suitable for Mg alloy AM technology could improve the manufacturing rate and enhance both strength and ductility through grain refinement. However, water bath cooling is unsuitable for Mg alloy AM due to the risk of a combustion reaction between high-temperature Mg and water, and the formation of pores caused by a drastic decrease in hydrogen solubility during solidification [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTherefore, we focused on a solid contact-based active cooling (SCAC) system that directly contacts a solid cooling medium with the molten metal. SCAC uses materials with high thermal conductivity such as pure copper or devices with high heat dissipation efficiency as the cooling medium. Zhang et al. improved the strength, grain refinement, and reduced the porosity of Al-Si alloy fabricated walls by SCAC employing a pure copper plate [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Li et al. improved the manufacturing rate and surface quality of 2325 Al alloy fabricated walls using thermoelectric cooling technology [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Additionally, Ma et al. used a water-cooling plate (material unspecified) to improve the cooling rate, grain refinement, and strength and ductility of AZ31 fabricated walls [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In our previous study, AZ31 walls were fabricated by no active cooling (NAC), an SCAC with a pure copper block (SCAC-C), and an SCAC with a copper block that had an internal water circulation mechanism (SCAC-W) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. We clarified how the placement of the copper blocks and the processing conditions affect arc deflection, droplet transfer, geometrical accuracy, and the temperature of the fabricated walls and the copper blocks.\u003c/p\u003e\u003cp\u003eAs described above, although there are very few research examples, SCAC has been reported to improve the manufacturing rate and mechanical properties of fabricated components. It is expected to be an effective active cooling technique for active metals such as aluminum (Al) and titanium (Ti) alloys, that are not suitable for direct water cooling. SCAC can also help avoid hydrogen embrittlement\u0026mdash;a risk associated with direct water cooling. Currently, SCAC is only used for fabricating wall structures; however, it could create free-form shapes by developing a roller-based cooling medium instead of a plate. Xie et al. fabricated a meter-sized turbine blade-like structure by rolling the sides of the bead with two rollers, though not for the purpose of active cooling [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTo demonstrate the effectiveness of SCAC, it is particularly important to achieve a high manufacturing rate of DED-fabricated components while maintaining their quality. However, to the best of our knowledge, the impacts of actively increasing the manufacturing rate (reducing the dwell time between layers) on the mechanical properties of the components have not yet been clarified. For instance, Zhao et al. have continuously fabricated a large-scale shell-shaped Al-Si alloy component with a total of 753 layers and high geometric accuracy by optimizing the process parameters without active cooling [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Although not explicitly stated in the paper, the manufacturing rate is estimated to be 317 cm\u0026sup3;/h. In contrast, the manufacturing rates in all prior SCAC studies are below 300 cm\u0026sup3;/h as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eTherefore, this study investigates the effects of reducing the dwell time between layers and SCAC on the tensile properties of the AZ31 wall. The maximum manufacturing rate adopted in this study is 364 cm\u0026sup3;/h. To examine the cooling rate of the AZ31 walls, we measured the temperature history, the geometric accuracy, and the grain size of the fabricated wall or the cooling media used. Additionally, we discussed the potential of SCAC to further increase the manufacturing rate of the wire-arc DED.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparisons among the manufacturing rates of wire-arc DED components with and without active cooling methods.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProcess\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMaterial\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eManufacturing\u003c/p\u003e\u003cp\u003erate\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWire \u003c/p\u003e\u003cp\u003ediameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eWire feed speed\u003c/p\u003e\u003cp\u003e\u003cem\u003eWFS\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eTravel speed\u003c/p\u003e\u003cp\u003e\u003cem\u003eTS\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eDwell\u003c/p\u003e\u003cp\u003etime\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eBead length\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eAnnotation and references\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e[cm\u003csup\u003e3\u003c/sup\u003e/h]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e[mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[m/min]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e[mm/min]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[s]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e[mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNatural\u003c/p\u003e\u003cp\u003ecooling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eER4043\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e317\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.2d\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e618\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eWFS and TS were the average values calculated from Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e of the cited paper [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eActive\u003c/p\u003e\u003cp\u003ecooling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWE43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e271\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e300\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eActive\u003c/p\u003e\u003cp\u003ecooling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAZ31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e229\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e450\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e70?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e100?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eThe bead length was estimated from the substrate dimensions (120 mm). The dwell time was estimated from Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e in the cited paper [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eActive\u003c/p\u003e\u003cp\u003ecooling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2325\u003c/p\u003e\u003cp\u003eAl alloy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.0\u0026times;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e300\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eDwell time was calculated from the cooling time (2880 s) and number of layers (37 layers) specified in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e of the cited paper [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"2. Experimental methods","content":"\u003ch2\u003e2.1 Material used\u003c/h2\u003e\n\u003cp\u003eTable 2 presents the nominal chemical compositions of the wire and the substrate used equivalent to the AZ31-Mg alloy. The wire has a diameter of 1.2mm, and the dimensions of the substrate are 150 \u0026times; 40 \u0026times; 5 mm. Table 3 shows the physical properties of the copper blocks used as the cooling medium. The copper blocks are equivalent to the JIS standard C1100P.\u003c/p\u003e\n\u003cp\u003eTable 2. Nominal chemical composition of the wire and the substrate used (wt.%).\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAl\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eZn\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMn\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSi\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFe\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNi\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMg\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12px;\"\u003e\n \u003cp\u003eBal.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 3. Physical properties of the copper blocks used as the cooling medium equivalent to the JIS standard C1100P.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eProperties\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eSpecific heat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[-]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e385\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eCoefficient of expansion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[10\u003csup\u003e\u0026minus;6\u003c/sup\u003e\u0026middot;K]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e17.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eThermal conductivity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[W/(m\u0026middot;K)]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e391\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eElectroconductivity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[%IACS]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e\u0026ge; 97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eLiquidus temperature\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[\u0026deg;C]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e1083\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eSolidus temperature\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e[\u0026deg;C]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 32px;\"\u003e\n \u003cp\u003e1065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e2.2 Fabrication process\u003c/h2\u003e\n\u003cp\u003eThe welding power source was a MIG welder (WB-P500L, DAIHEN Corp.). The wire-arc DED system consists of three orthogonal axes and CNC device that controls the trajectory of the welding torch (BTA300-30, DAIHEN Corp.), which is attached to the Z-axis plate. Fig. 1 shows a schematic diagram of the active cooling system. An Mg alloy straight bead was deposited in the gap between two parallel copper blocks (Fig. 1(a)). During the arc-off period, the copper blocks were raised to match the layer height, maintaining contact between the molten Mg and the copper blocks. Repeating these steps fabricated a wall component with a height of approximately 60 mm, a length of approximately 100 mm (with 80 mm path length), and a width of approximately 14 mm. Note that the molten Mg did not bond to the copper blocks in all deposition processes.\u003c/p\u003e\n\u003cp\u003eThe copper blocks used for SCAC-C were shaped 200 \u0026times; 15 \u0026times; 15 mm in size (Fig. 1(b)). The copper blocks used for SCAC-W were 200 \u0026times; 22 \u0026times; 22 mm with a central long hole of \u0026Phi;14.5 mm (Fig. 1(c)). Water tube adapters and hoses connected the blocks to an external water tank. An electric pump circulated cooling water at approximately 12\u0026deg;C inside the blocks. The volumetric flow rate of the cooling water was 3\u0026times;10\u003csup\u003e\u0026minus;4\u003c/sup\u003e m\u0026sup3;/s, and the flow velocity was 1.9 m/s.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 4 shows the common processing parameters. The welding mode was a direct current pulse. Compared to other AM fabrication examples, a very high material feed rate of 774 cm\u003csup\u003e3\u003c/sup\u003e/h was used. Argon gas with a concentration of at least 99.9% was used as shielding gas. Table 5 shows the individual processing parameters. The interpass dwell time (\u003cem\u003et\u003c/em\u003e) for each layer was either 60 s or less or 120 s or more. The manufacturing rate with \u003cem\u003et\u003c/em\u003e =18 s is 364 cm\u003csup\u003e3\u003c/sup\u003e/h. The abbreviations defined in this paper\u0026mdash;NAC, SCAC-C, and SCAC-W\u0026mdash;are synonymous with FCC (free convection cooling), SCAC, and SCACW, respectively, as described in our previous study [19].\u003c/p\u003e\n\u003cp\u003eTable 4. Common processing parameters.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003eUnit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eValue\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eAverage output current\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[A]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e106\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eWire feed speed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[mm/min]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e11.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eDeposition rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e[cm\u003csup\u003e3\u003c/sup\u003e/h]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e774\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eTravel speed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[mm/min]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eWelding torch to work distance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e12.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003ePath length along X axis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 55px;\"\u003e\n \u003cp\u003eFlow rate of shielding Ar gas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e[L/min]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 5. Individual processing parameters.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003eTest\u0026nbsp;\u003cbr\u003e\u0026nbsp;No.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eCooling method\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cem\u003eW\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eAverage output voltage \u003cem\u003eU\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eDwell time per layer \u003cem\u003et\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eManufacturing rate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e[mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e[V]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e[s]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e[cm\u003csup\u003e3\u003c/sup\u003e/h]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003eNAC (No active cooling)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e18.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e213\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003eNAC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e18.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e126\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eNAC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e213\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003eNAC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSCAC-C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e364\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSCAC-C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e132\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e84\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSCAC-W\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e364\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 9px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSCAC-W\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e22.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e126\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20px;\"\u003e\n \u003cp\u003e87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e2.3 Measurement of grain size and tensile properties\u003c/h2\u003e\n\u003cp\u003eFig. 2 illustrates the method used to evaluate the grain size and the geometry of the tensile test specimen. Fig. 2(a) shows an actual image of the fabricated wall and the sampling location for microstructure observation. The central portion of the fabricated wall was cut using electrical discharge machining (EDM). The cross-section of the resin-embedded specimen in the Y-Z plane was polished using SiC abrasive paper with #1000 and #2000 grit, as well as diamond suspensions with 6 \u0026micro;m and 1 \u0026micro;m particle sizes. The polished surface of the specimen was then etched for approximately 20 seconds in a room-temperature solution containing 5 g of picric acid, 5 mL of acetic acid, 10 mL of purified water, and 100 mL of ethanol to reveal the grain boundaries (Fig. 2(b, c)). The grain size measurement area was the center of the wall in the Y-Z plane (-0.5 mm \u0026lt; Y \u0026lt; 0.5 mm). Grain size in the height direction was evaluated by determining the intersections of three 10-mm-long test lines crossing the heat-affected zone (HAZ) and fusion zone with the grain boundaries (Fig. 2(c)) using a digital microscope (VHX-6000, Keyence Corp.).\u003c/p\u003e\n\u003cp\u003eThe tensile test specimens were cut from the center of the fabricated wall using EDM such that the tensile direction was parallel to the build height. The geometry of the tensile test specimen is shown in Fig. 2(d). The length, width, and thickness of the parallel section were 30.1 mm, 5 mm, and 3.1 mm, respectively. Tensile tests were performed at room temperature using a universal testing machine (Z100 THW 100kN, Zwick Roell Corp.). The representative value for each condition was taken as the average value of more than six test results where fracture occurred in the parallel section.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003ch2\u003e3.1 Temperature of copper block and wall components\u003c/h2\u003e\n\u003cp\u003eFig. 3 illustrates the temperature measurements of the copper block during arc discharge using a thermal camera (T630sc, Teledyne FLIR LLC). The temperature history shows the average temperature at the center of the copper block\u0026rsquo;s surface. The block was pre-coated with a black body spray (emissivity 0.94) as shown in Fig. 3(a). Figs. 3(c, d, e) show the average temperature histories of the copper blocks for Nos. 6 (SCAC-C, \u003cem\u003et\u003c/em\u003e = 132 s), 5 (SCAC-C, \u003cem\u003et\u003c/em\u003e = 18 s), and 7 (SCAC-W, \u003cem\u003et\u003c/em\u003e = 18 s), respectively.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 3(c), it is evident that the copper block temperature increased with the number of layers under the SCAC-C with a relatively long \u003cem\u003et\u003c/em\u003e. However, the temperature history from the 11\u003csup\u003eth\u003c/sup\u003e layer onwards was generally consistent. This is because a balance was established between the heat input from the arc discharge and the increased heat dissipation from the sidewall with each additional layer. With a short \u003cem\u003et\u003c/em\u003e (No. 5, Fig. 3(d)), the temperature of the copper block was significantly higher than that of No. 6. Comparing the temperature histories of the 12\u003csup\u003eth\u003c/sup\u003e and 18\u003csup\u003eth\u003c/sup\u003e layers reveals that the interpass temperature of the copper block immediately prior to arcing increased from approximately 410\u0026deg;C to 500\u0026deg;C, while the maximum temperature increased from approximately 500\u0026deg;C to 570\u0026deg;C. In contrast, for the SCAC-W with a short \u003cem\u003et\u003c/em\u003e (No. 7, Fig. 3(e)), the copper block temperature only increased by approximately 10\u0026deg;C even as the number of layers increased.\u003c/p\u003e\n\u003cp\u003eFig 3(b) shows the transition of the maximum temperature of the copper block for each layer. The average maximum temperatures from the 12\u003csup\u003eth\u003c/sup\u003e to 14\u003csup\u003eth\u003c/sup\u003e layers for Nos. 5, 6, 7, and 8 were 518\u0026deg;C, 232\u0026deg;C, 22\u0026deg;C, and 32\u0026deg;C, respectively. These results demonstrate that the SCAC-W can largely maintain its initial temperature even with a dwell time of only 18 seconds.\u003c/p\u003e\n\u003cp\u003eFig. 4 shows the temperature measurement of the fabricated wall during the arc-off period. The emissivity of the AZ31 fabricated wall is difficult to identify because MIG welding of AZ31 generates a lot of black powder called smut. Therefore, instead of using a non-contact temperature sensor, the temperature of the top layer of the wall was measured with a K-type thermocouple (TH-8292-2, THREE HIGH CO.,LTD.) in direct contact with the wall (Fig. 4(a)). The measured walls were Nos. 4 (NAC, \u003cem\u003et\u003c/em\u003e = 150 s), 6 (SCAC-C, \u003cem\u003et\u003c/em\u003e = 132 s), and 8 (SCAC-W, \u003cem\u003et\u003c/em\u003e = 126 s). Their processing conditions were identical except for their cooling method and their interpass dwell time was relatively long.\u003c/p\u003e\n\u003cp\u003eFig. 4(b) shows the temperature history of the top layer after the 10\u003csup\u003eth\u003c/sup\u003e layer was deposited. 100 seconds after arc-off, the temperatures for Nos. 4, 6, and 8 were 129\u0026deg;C, 168\u0026deg;C, and 97\u0026deg;C, respectively. No. 6 (SCAC-C) had the highest temperature. This is due to the contact heat transfer from the copper blocks, which was heated to over 150\u0026deg;C. However, the cooling rate of No. 6 during arc-on may be higher than that of No. 4 (NAC) because the temperature of No. 6 was lower than that of NAC 30 seconds after arc-off. As shown in Fig.4 (b), the cooling rates for Nos. 6 and 8 (SCAC-W) were 0.91\u0026deg;C/s and 1.25\u0026deg;C/s, respectively, 60 seconds after arc-off. Fig. 4(c) shows the temperature measurement for each layer 40 seconds after arc-off. The average temperatures from 10\u003csup\u003eth\u003c/sup\u003e to 12\u003csup\u003eth\u003c/sup\u003e layers for Nos. 4, 6, and 8 were 209\u0026deg;C, 196\u0026deg;C, and 148\u0026deg;C, respectively.\u003c/p\u003e\n\u003cp\u003eFrom the above, we clarified that SCAC-W can effectively lower the temperature of the copper block and the fabricated wall. To understand the effects of the active cooling method on the microstructure, it is essential to measure the temperature data near the molten pool during arc-on, including maximum temperature, holding time, and cooling rate above recrystallization temperature. Section 3.3 will discuss the cooling rate for the fabricated walls with a short interpass dwell time, such as Nos. 5 and 7, based on the grain size observation results.\u003c/p\u003e\n\u003ch2\u003e3.2 Surface quality\u003c/h2\u003e\n\u003cp\u003eFig. 5 illustrates the scan data of all the fabricated walls, which were acquired using a 3D coordinate measuring machine (VL300, Keyence Corp.). The color maps indicate the difference between the average Y-coordinate within the inspection range and the point cloud for each side surface of the wall. Deep concavities with a difference of -1 mm or less are shown in blue, while large convexities with a difference of 1 mm or more are shown in red. The side surface roughness of the wall was evaluated by the arithmetic mean height (Sa), which is calculated using the following equation:\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58895_8739fc6c57c1c19a/58895_custom_files/img1762531784.png\" width=\"468\" height=\"76\"\u003e\u003c/p\u003e\n\u003cp\u003eAs shown in the NAC walls (Fig. 5(a-d)), weld sagging frequently occurred and surface roughness increased with an increase in welding voltage and a decrease in interpass dwell time. In particular, for No. 3 (NAC, 22.4 V, \u003cem\u003et\u003c/em\u003e = 42 s), the molten pool became oversized and flowed in the width direction (Y-axis), making further deposition difficult. Therefore, deposition was stopped at the 12\u003csup\u003eth\u003c/sup\u003e layer. These results highlight the importance of setting appropriate heat input conditions, such as an interpass dwell time to achieve a near-net shape through natural cooling.\u003c/p\u003e\n\u003cp\u003eFor the SCAC-C walls (Fig. 5(e, f)), the surface roughness decreased to 0.09 mm as the interpass dwell time decreased. Continuous heat input raised the temperature around the molten pool. This resulted in the molten metal with low surface tension spreading over the entire space between the copper blocks. A similar trend was observed for the SCAC-W walls (Fig. 5(g, h), though the overall surface roughness was lower than that of the SCAC-C walls. This is due to increased kinematic viscosity and decreased wettability of the molten metal, which were caused by higher cooling rate and lower temperature of the fabricated walls. These results do not indicate a decrease in geometrical accuracy for SCAC-W; rather, they show that the fabricated wall can be sufficiently cooled with a short interpass dwell time.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTherefore, SCAC-W has the potential to be applied to a wire-arc DED process with an even shorter interpass dwell time (\u003cem\u003et\u003c/em\u003e \u0026lt; 18 s). In contrast, the copper block temperature can increase further for SCAC-C, which may cause the cooling rate of the fabricated wall to drop below that of NAC.\u003c/p\u003e\n\u003ch2\u003e3.3 Microstructure\u003c/h2\u003e\n\u003cp\u003eFig. 6 shows the microstructure images and grain size distribution maps for Nos. 3, 4, 5, and 7, all with a welding voltage of 22.4V. A sufficiently wide inspection area was evaluated, with approximately 300 to 900 grains examined. As the microstructure images in Figs. 6(c, e, g) show, the grains in the HAZ are coarser than those in the fusion zone, regardless of the cooling method. The grains in No. 3 (NAC, \u003cem\u003et\u003c/em\u003e = 42 s), where significant weld sagging occurred, were the largest among all processing conditions (Figs. 6(a, b)). The average grain size was 148 \u0026micro;m and the grains larger than 280 \u0026micro;m accounted for 7% of the total. Please note that the boundary between the HAZ and the fusion zone was unclear; therefore, the boundary line is not indicated in the image. In No. 4 (NAC, \u003cem\u003et\u003c/em\u003e = 150 s), the grains were more refined than in No. 3. The average grain size was 67 \u0026micro;m and no grains larger than 280 \u0026micro;m were observed in the inspection area (Figs. 6(c, d)).\u003c/p\u003e\n\u003cp\u003eIn Nos. 5 (SCAC-C,\u003cem\u003e\u0026nbsp;t\u003c/em\u003e = 18 s) and 7 (SCAC-W,\u003cem\u003e\u0026nbsp;t\u003c/em\u003e = 18 s), grain refinement was observed throughout the entire inspection area, despite the significantly shorter interpass dwell time compared to No. 4. The average grain size of No. 5 was 58 \u0026micro;m. This result suggests that the contact heat transfer from the copper block, which was heated to an interpass temperature of 500\u0026deg;C (Fig. 3(d)), provided the fabricated wall with a higher cooling rate than the heat transfer from the NAC wall to the atmosphere. The average grain size of No. 7 was 43 \u0026micro;m, which was the smallest among the four conditions shown in Fig. 6. It is believed that the cooling rate of the fabricated wall improved due to heat transfer from the water-cooled copper block which remained below 50\u0026deg;C.\u003c/p\u003e\n\u003cp\u003eThe change in grain size in the width direction (Y-axis) was measured. Fig. 7 shows the macro- and microstructures in the HAZ of No. 7 (SCAC-W, \u003cem\u003et\u003c/em\u003e = 0.3 min). Magnified microstructure images of regions b and c in Fig. 7(a) are shown in Figs. 7(b, c), respectively. Similarly, magnified images of regions d and e in Fig. 7(c) are shown in Figs. 7(d, e), respectively. The observation images shown in Figs. 7(d, e) are approximately 550 \u0026micro;m \u0026times; 730 \u0026micro;m in size. To evaluate the aspect ratio, three test lines were drawn in both the width and height directions (Y- and Z-axes). The grain size measurement results along the width direction are shown in Fig. 7(f).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe average grain size at the center of the fabricated wall was 80 \u0026micro;m, with an aspect ratio of approximately 1.2 (ratio of grain size in the height direction relative to the width direction). This indicates that the grains grew slightly in the build height direction (Fig. 7(e)). Since the heat transfer direction inside a wire-arc DED-fabricated component is predominantly in the height direction, the grains in the central part tend to grow in that direction. In contrast, the average grain size near the side surface was 47 \u0026micro;m with an aspect ratio of approximately 1.0. The grains refined into an equiaxed shape along the width direction as shown in Figs. 7(d, f). A characteristic columnar structure was also observed near the side surface (Fig. 7(b)). This occurred because a high-temperature gradient was generated at the interface where the copper block met the molten metal. This gradient caused the grains to grow toward the copper block. However, this structure was only observed within a limited region (300 \u0026micro;m) near the side surface where a relatively large, flat surface formed. The columnar structure was not observed under other conditions. Even in No. 8, most of the microstructure near the side surface was equiaxed, as shown in Fig. 7(d).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e3.4 Tensile test\u003c/h2\u003e\n\u003cp\u003eFig. 8 presents the results of the tensile tests. The bar graphs illustrate the average values, and the error bars indicate the standard deviation. For NAC, ultimate tensile strength (UTS), 0.2% yield strength (YS), and elongation (EL) all decreased as the interpass dwell time shortened. In contrast, a significant reduction in interpass dwell time (from 132 s to 18 s) caused a 2-3% decrease in EL for SCAC-C and SCAC-W, but had no significant effect on UTS or YS. Comparing conditions with relatively similar interpass dwell times (\u003cem\u003et\u0026nbsp;\u003c/em\u003e\u0026lt; 60 s or \u003cem\u003et\u003c/em\u003e \u0026gt; 120 s) reveals that both strength and ductility improved in the order of SCAC-W \u0026gt; SCAC-C \u0026gt; NAC. This trend aligns with previous studies reporting improvements in tensile properties due to grain refinement [13, 22\u0026ndash;24].\u003c/p\u003e\n\u003cp\u003eAlthough the mechanical properties of magnesium alloys depend strongly on grain size, other factors―texture, microscopic orientation factors, and the morphology of eutectic compounds―can also influence them. Kamado et al. [9] reported that the tensile strength and ductility of the as-cast MC2 magnesium alloy were enhanced by both a reduction in the volume fraction of eutectic compounds and a blocky precipitation of these compounds near the three-grain junctions of the cell boundaries. Similarly, Li et al. [18] found that the strength enhancement of an active-cooled AZ31 wall is due to grain refinement strengthening and precipitation strengthening from the formation of nano-sized particles. Furthermore, Yoshida et al. [25] reported that the ductility of AZ31 significantly improved after equal-channel angular extrusion. This improvement was attributed to the activation of cross-slip from the basal plane to non-basal planes, in addition to basal slip. Therefore, a comprehensive investigation into the effects of active cooling on microstructural factors and crystal orientation is essential for future research.\u003c/p\u003e\n\u003cp\u003eIn summary, we clarified that active cooling improves both the manufacturing rate and the mechanical properties. Due to the limitations of our experimental setup, the minimum interpass dwell time was 18 seconds. However, SCAC-W (No. 7, \u003cem\u003et\u003c/em\u003e = 18 s) were able to maintain the copper block temperature below 50℃. Additionally, the grains of the SCAC-C walls (No. 5, \u003cem\u003et\u003c/em\u003e = 18 s) were finer than those in NAC walls, even when the copper blocks were heated to an interpass temperature of 500\u0026deg;C. Therefore, we believe that SCAC-W can prevent grain coarsening and the degradation of mechanical properties even with significantly shorter interpass dwell times (higher manufacturing rates).\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, AZ31-walled components were fabricated by wire-arc DED with and without solid contact-based active cooling (SCAC). The temperature histories, side surface geometries, and microstructures of the fabricated walls were comprehensively evaluated. Finally, we examined the effects of SCAC and a shortened interpass dwell time on cooling rate and the tensile properties of AZ31 walls. Here are main conclusions:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eFor no active cooling (NAC), frequent weld sagging occurred, and the grain size became coarser with a shorter interpass dwell time from 150 s to 42 s.\u003c/li\u003e\n \u003cli\u003eFor SCAC using copper blocks (SCAC-C), the interpass temperature of the copper block increased to 500\u0026deg;C with a significant reduction in interpass dwell time (from 132 s to 18 s). However, the grains were finer than NAC with a long interpass dwell time.\u003c/li\u003e\n \u003cli\u003eFor SCAC with an internal water circulation (SCAC-W), the copper block temperature was consistently maintained below 50\u0026deg;C, even with a reduction in interpass dwell time (from 126 s to 18 s). The fabricated walls had the finest microstructure among all processing conditions, and a columnar structure was also observed in a localized region near the contact surface with the copper blocks.\u003c/li\u003e\n \u003cli\u003eThe ultimate strength, yield strength, and elongation of the fabricated walls increased in the following order: SCAC-W \u0026gt; SCAC-C \u0026gt; NAC. The measurement results of the copper block temperature in the SCAC-C and SCAC-W processes suggest that SCAC-W can prevent grain coarsening and the degradation of tensile properties even with significantly shorter interpass dwell times.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Declarations","content":"\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis work was supported by The Japan Welding Engineering Society and The Light Metal Educational Foundation.\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eH. Nagamatsu: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, validation, visualization, writing\u0026mdash;original draft, writing\u0026mdash;re-view \u0026amp; editing. H. Sasahara: funding acquisition, investigation, project administration, resources, supervision, writing\u0026mdash;re-view \u0026amp; editing\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData availability\u003c/p\u003e\n\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the article and/or its supplementary materials.\u003c/p\u003e\n\u003cp\u003eAcknowledgments\u003c/p\u003e\n\u003cp\u003eWe would like to acknowledge Japan Fine Steel Co., Ltd. for supplying the AZ31 wire; Prof. T. Kuboki and Associate prof. S. Kajikawa for permission me to use the universal testing machine and J. Kinoshita for his help developing the cooling device.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eManjhi SK, Sekar P, Bontha S, Balan ASS (2024) Additive manufacturing of magnesium alloys: Characterization and post-processing. International Journal of Lightweight Materials and Manufacture 7:184\u0026ndash;213. https://doi.org/10.1016/j.ijlmm.2023.06.004\u003c/li\u003e\n\u003cli\u003eLi Y, Yin S, Zhang G, et al (2024) A Review on Wire Arc Additive Manufacturing of Magnesium Alloys: Wire Preparation, Defects and Properties. Met Mater Int. https://doi.org/10.1007/s12540-024-01724-7\u003c/li\u003e\n\u003cli\u003eAsadi P, Kazemi-Choobi K, Elhami A (2012) Welding of Magnesium Alloys. In: New Features on Magnesium Alloys. IntechOpen\u003c/li\u003e\n\u003cli\u003eFang X, Yang J, Wang S, et al (2022) Additive manufacturing of high performance AZ31 magnesium alloy with full equiaxed grains: Microstructure, mechanical property, and electromechanical corrosion performance. Journal of Materials Processing Technology 300:117430. https://doi.org/10.1016/j.jmatprotec.2021.117430\u003c/li\u003e\n\u003cli\u003eGuo Y, Quan G, Jiang Y, et al (2021) Formability, microstructure evolution and mechanical properties of wire arc additively manufactured AZ80M magnesium alloy using gas tungsten arc welding. Journal of Magnesium and Alloys 9:192\u0026ndash;201. https://doi.org/10.1016/j.jma.2020.01.003\u003c/li\u003e\n\u003cli\u003eWang P, Zhang H, Zhu H, et al (2021) Wire-arc additive manufacturing of AZ31 magnesium alloy fabricated by cold metal transfer heat source: Processing, microstructure, and mechanical behavior. Journal of Materials Processing Technology 288:116895. https://doi.org/10.1016/j.jmatprotec.2020.116895\u003c/li\u003e\n\u003cli\u003eCao Q, Zeng C, Cai X, et al (2023) High-strength Mg-10Gd-3Y-1Zn-0.5Zr alloy fabricated by wire-arc directed energy deposition: Phase transformation behavior and mechanical properties. Additive Manufacturing 76:103789. https://doi.org/10.1016/j.addma.2023.103789\u003c/li\u003e\n\u003cli\u003eHeinrich L, Feldhausen T, Saleeby K, et al (2023) Build plate conduction cooling for thermal management of wire arc additive manufactured components. Int J Adv Manuf Technol 124:1557\u0026ndash;1567. https://doi.org/10.1007/s00170-022-10558-9\u003c/li\u003e\n\u003cli\u003eKamado S, Tsukuda M, Tokutomi I, Hirose K (1987) Effect of solidification conditions on mechanical properties of unidirectionally solidified AZ91C alloy. Journal of Japan Institute of Light Metals 37:721\u0026ndash;728. https://doi.org/10.2464/jilm.37.721\u003c/li\u003e\n\u003cli\u003eWang X, Wang A, Li Y (2020) Study on the deposition accuracy of omni-directional GTAW-based additive manufacturing. Journal of Materials Processing Technology 282:116649. https://doi.org/10.1016/j.jmatprotec.2020.116649\u003c/li\u003e\n\u003cli\u003eKumar P, Sharma SK, Raj Singh RK (2023) Effect of cooling media on bead geometry, microstructure, and mechanical properties of wire arc additive manufactured IN718 alloy. Adv Manuf. https://doi.org/10.1007/s40436-023-00457-x\u003c/li\u003e\n\u003cli\u003eJorge VL, Scotti FM, Teixeira FR, et al (2025) Application of near-immersion active cooling for thermal management in arc additive manufacturing of thin super duplex stainless steel walls. Int J Adv Manuf Technol 137:3025\u0026ndash;3048. https://doi.org/10.1007/s00170-025-15355-8\u003c/li\u003e\n\u003cli\u003eHauser FE, London PR, Dorn JE (1956) Fracture of Magnesium Alloys at Low Temperature. JOM 8:589\u0026ndash;592. https://doi.org/10.1007/BF03377735\u003c/li\u003e\n\u003cli\u003eChino Y, Mabuchi M (2001) Plastic-forming processes for magnesium alloys. Journal of Japan Institute of Light Metals 51:498\u0026ndash;502. https://doi.org/10.2464/jilm.51.498\u003c/li\u003e\n\u003cli\u003eLukac P, Trojanova Z (2011) INFLUENCE OF GRAIN SIZE ON DUCTILITY OF MAGNESIUM ALLOYS. Materials Engineering 18:\u003c/li\u003e\n\u003cli\u003eZhang A, Xing Y, Yang F, et al (2021) Development of a New Cold Metal Transfer Arc Additive Die Manufacturing Process. Advances in Materials Science and Engineering 2021:1\u0026ndash;15. https://doi.org/10.1155/2021/9353820\u003c/li\u003e\n\u003cli\u003eLi F, Chen S, Shi J, et al (2018) Thermoelectric cooling-aided bead geometry regulation in wire and arc-based additive manufacturing of thin-walled structures. Applied Sciences (Switzerland) 8:207. https://doi.org/10.3390/app8020207\u003c/li\u003e\n\u003cli\u003eMa P, Wang C, Jia H, et al (2025) Simultaneous enhancement in deposition efficiency and nano-scale precipitation of high-strength AZ31 Mg alloy via water cooling assisted wire-arc directed energy deposition. Thin-Walled Structures 206:112689. https://doi.org/10.1016/j.tws.2024.112689\u003c/li\u003e\n\u003cli\u003eNagamatsu H, Sasahara H (2022) Improvement of Cooling Effect and Dimensional Accuracy of Wire and Arc Additive Manufactured Magnesium Alloy by Active-Cooling-Based Contacting Copper Blocks. Journal of Manufacturing and Materials Processing 6:27. https://doi.org/10.3390/jmmp6020027\u003c/li\u003e\n\u003cli\u003eXie Y, Zhang H, Zhou F (2016) Improvement in Geometrical Accuracy and Mechanical Property for Arc-Based Additive Manufacturing Using Metamorphic Rolling Mechanism. Journal of Manufacturing Science and Engineering 138:111002. https://doi.org/10.1115/1.4032079\u003c/li\u003e\n\u003cli\u003eZhao Y, Jia Y, Chen S, et al (2020) Process planning strategy for wire-arc additive manufacturing: Thermal behavior considerations. Additive Manufacturing 32:100935. https://doi.org/10.1016/j.addma.2019.100935\u003c/li\u003e\n\u003cli\u003eLi K, Li B, Zhu L, et al (2024) Optimizing microstructure and strength of CMT-wire arc additive manufactured WE43 Mg alloy through a novel active cooling technique. Thin-Walled Structures 205:112453. https://doi.org/10.1016/j.tws.2024.112453\u003c/li\u003e\n\u003cli\u003eWei J, He C, Qie M, et al (2023) Achieving high performance of wire arc additive manufactured Mg\u0026ndash;Y\u0026ndash;Nd alloy assisted by interlayer friction stir processing. Journal of Materials Processing Technology 311:117809. https://doi.org/10.1016/j.jmatprotec.2022.117809\u003c/li\u003e\n\u003cli\u003eJ. A. CHAPMAN, D. V. WILSON (1962) The room-Temperature Ductility of Fine-Grain Magnesium. JOURNAL OF THE INSTITUTE OF METALS 91:39\u0026ndash;40\u003c/li\u003e\n\u003cli\u003eKobayashi T, Koike J, Yoshida Y, et al (2003) Grain Size Dependence of Active Slip Systems in an AZ31 Magnesium Alloy. JJapan InstMetals 67:149\u0026ndash;152. https://doi.org/10.2320/jinstmet1952.67.4_149\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"additive manufacturing, magnesium alloy, active cooling, dwell time, microstructure, tensile properties","lastPublishedDoi":"10.21203/rs.3.rs-7770019/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7770019/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWire-arc directed energy deposition (DED) has been a promising additive manufacturing technology for safety and rapidly fabricating magnesium (Mg) alloy components. However, high heat input from the electric arc can degrade geometric accuracy and cause grain coarsening. This is a critical issue for Mg alloys because their mechanical properties are strongly influenced by grain size. One common solution is to pause the deposition process until the component cools to an appropriate temperature, which significantly reduces the manufacturing rate. To address this issue, our study proposes a novel active cooling method for the Mg alloy deposition process: solid-contact active cooling (SCAC). This method involves direct contact between copper blocks and the fabricated component. We fabricated AZ31 alloy walled components using three cooling methods: no active cooling (NAC), SCAC with copper blocks (SCAC-C), and SCAC with internal water circulation (SCAC-W). The manufacturing rate reached up to 364 cm³/h. NAC with a short interpass dwell time resulted in frequent weld sagging, coarser grains, and decreased tensile properties. In contrast, SCAC-C with a short interpass dwell time led to finer grains and improved surface quality, even though the copper blocks reached 500℃. The SCAC-W was the most effective, as the water-cooled copper blocks remained below 50℃, resulting in the finest grains and the best tensile properties. These results demonstrate that the SCAC method, particularly the SCAC-W, can prevent grain coarsening and degradation of tensile properties while achieving a significantly higher manufacturing rate.\u003c/p\u003e","manuscriptTitle":"Effect of the active cooling and dwell time to tensile properties of AZ31 wall components by wire-arc directed energy deposition","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-07 16:16:08","doi":"10.21203/rs.3.rs-7770019/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2025-12-19T20:07:59+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-11-13T15:48:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-27T14:52:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-11T11:06:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2025-10-09T20:38:13+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f2845847-f166-4867-bab0-b0ccaee5f242","owner":[],"postedDate":"November 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-07T16:04:32+00:00","versionOfRecord":{"articleIdentity":"rs-7770019","link":"https://doi.org/10.1007/s00170-026-17843-x","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2026-04-01 15:58:11","publishedOnDateReadable":"April 1st, 2026"},"versionCreatedAt":"2025-11-07 16:16:08","video":"","vorDoi":"10.1007/s00170-026-17843-x","vorDoiUrl":"https://doi.org/10.1007/s00170-026-17843-x","workflowStages":[]},"version":"v1","identity":"rs-7770019","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7770019","identity":"rs-7770019","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}