Autogenous laser welding of high Mn lightweight steel for automotive applications

Autogenous laser welding of high Mn lightweight steel for automotive applications | 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 Autogenous laser welding of high Mn lightweight steel for automotive applications Giacomo Villa, Silvia Barella, Davide Mombelli, Andrea Gruttadauria, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9573879/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Lightweight steels are an innovative steel grade whose research is very interesting for application in automotive sector. They are featured by high Mn and Al content, high mechanical properties (up to 800MPa of yield strength and up to 55% of elongation at break) and low density (13% lower than conventional stainless steel). Especially because of the application sector, the assessment of these alloys weldability is of outmost importance. Due to the high content chemical elements different criticalities are expected, as Mn evaporation and κ-carbides precipitation. The former may lead to inhomogeneous chemical composition and so different microstructure, mechanical properties and difference response to welding process. The latter is the most studied strengthening method in this class of steel, but it may lead to excessive ductility loss. An austenitic with high Mn lightweight steel alloy has been tested with Laser Beam Welding with different configurations and different material conditions. Microstructure and mechanical properties of the welded joints has been investigated. Solid welded joints were obtained, but significant macro-porosity was observed in the hot rolled material. In the WZ, both a dendritic and columnar microstructure has been observed, while an extremely narrow grain coarsened-HAZ have been detected. In the WZ a limited softening has been observed in the material after solubilization while in the hot rolled one, the difference is more marked. Uniaxial tensile test has highlighted the macro-porosity effect in the HR samples while it has provided good results in the SOL samples. Welding Light steel laser Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Introduction Many sectors are pushing toward a reduction of emissions and energy consumption and, especially in transport, weight reduction is fundamental to achieve considerable energy savings [ 1 , 2 ]. Classically weigh reduction is obtain by means of lower density alloys (e.g., Al) or the use of alloys with higher strength (e.g., Ultra-High Strength Steel) [ 3 – 5 ]. In both cases pros and cons are to be considered such as more energy consuming production and difficulties in the joining for Al [ 6 , 7 ] and excessive thickness reduction in case of UHSS. The pros of lighter material and higher strength could be combined in innovative lightweight steels alloys. Such alloys are featured by low density (10% lower than high strength steels, 15% lower than Hadfield steels and AISI 304, and 16% lower than AISI 316) and high mechanical strength (up to 1500MPa ultimate tensile stress -UTS- and 80% elongation at break) [ 8 , 9 ]. Such properties are obtained balancing between the main alloying elements: Mn, Al, and C. They point out ferritic, austenitic, or duplex microstructure featured by different properties [ 8 , 9 ]. The austenitic microstructure is obtained by Al concentration of ~ 5–12%, Mn of ~ 12–30% and C of ~ 0.6-2% and they have UTS of ~ 800–1500 MPa and TE of ~ 30–80% [ 8 ]. These alloys’ most studied strengthening method is κ-carbides precipitation. Such carbides are featured by an E2 1 structure with a stoichiometric formula of (Fe,Mn) 3 AlC. In austenitic steels they can be intra-granular κ’ finely dispersed in the austenitic matrix, improving the mechanical properties, or they can be inter-granular κ*, as a second phase at grain boundaries having detrimental effects [ 10 – 12 ]. Considering the future application in automotive applications, it is of the upmost importance the weldability of these alloys. Some criticalities are expected due to the richness of the chemical composition and the material’s susceptibility to unwanted thermal treatments’ effects. Grain coarsening has been observed [ 13 – 15 ], but the most detrimental is undesired phases presence, as ferrite [ 16 – 20 ], κ-carbides [ 13 , 20 – 23 ] and b-Mn [ 24 ]. In addition, possible Mn evaporation during the melting procedure can be observed [ 24 – 26 ]. Due to material microstructure (fully austenitic) hot cracks in the weld metal and distortion of the workpiece may be observed [ 27 ]. Arc welding requires filler material to fill the root gap and to control the welds quality. In case of heterogeneous filler, it requires a deep research and investigation, and, in case of homogenous material, it requires to be manufactured in precise dimensions and in case of material still in research phase it might be difficult to shape the material accordingly [ 28 – 31 ]. Such necessities could be avoided via autogenous welding. Laser beam welding (LBW) could perform such type of welding [ 32 , 33 ], avoiding so time-consuming and costly development of filler material or manufactory of homogenous filler. This technology has become a pivotal technology in the automotive sector, particularly due to its precision, efficiency, and ability to handle advanced high-strength steels (AHSS). This technology is used in the automotive industry for body-in-white (BIW) assembly, including body frames, door frames, trunks, auto hoods, and chassis [ 34 ]. It is highly versatile, capable of welding various materials and thicknesses, and it is used for different joint types, such as butt joints, lap joints, and tailored blanks and it could be performed without contact. LBW systems are also highly compatible with automated production lines, enhancing efficiency and consistency in mass production [ 34 , 35 ]. Laser welding is particularly effective with high-strength materials, like AHSS, due to its ability to create strong joints with minimal heat-affected zones (HAZ) and extremely localized energy delivery, preserving the material properties [ 36 – 39 ]. Due to the possibilities given from laser automatization it is also possible to modify the laser beam path leading to wobbling strategies that can be beneficial in porosity reduction, microstructural control and, especially in case of autogenous welding, in gap bridging [ 40 , 41 ]. Although lightweight steels weldability is a topic of the upmost importance, limited studies have been presented and even less studies focused on laser beam welding technique [ 27 , 42 ]. In this study the weldability of a high Mn austenitic lightweight steel alloy has been investigated via laser beam welding. Different welding configuration (beam on plate and butt-welding) have been performed and different material conditions (as hot rolled and after solubilization) have been employed. The welded zone morphology and microhardness have been studied along with tensile properties of the welded material. Materials and methods In this study, weldability of an austenitic lightweight steel was investigated. The nominal composition and the one obtained by OES (optical emission spectroscopy) is reported in Table 1 . This material density was measured to be almost 6.7 g/cm 3 , so significantly lower than other commercial austenitic steels like AISI 304 or 316 (8 g/cm 3 ) and Hadfield steels (7.890 g/cm 3 ). Table 1 OES and nominal chemical composition wt.% Fe Mn Al C OES 59.7 ± 0.5 29.2 ± 0.5 8.6 ± 0.1 0.96 ± 0.04 Nominal 60 30 9 1 The material was studied in two conditions: hot rolled (labelled HR) and after solubilization, performed at 1000°C with holding time of 30min, (labelled SOL). The material was in the form of 5 mm thick plates for both conditions. Two different welding configurations were tested in this study performed via automatized LBW (as in Fig. 1 ). An initial test was performed with bead on plate (BoP) configuration to study the material response to LBW. In this part of the study the welding parameters was modified to reach satisfactory results in terms of weld seam geometry and hardness distribution. In this part of the study, only HR material was employed. In particular, laser welding with a stationary beam was compared to a wobbling weld with a circular trajectory. Laser power was varied in a relatively restricted region between 3.25 and 3.5 kW according to the results of preliminary tests not described here for brevity. The focal position was varied at -2.5, 5, and − 10 mm in order to employ larger spot diameters on the material surface, hence enlarging the melt pool. At these focal positions, the laser beam diameter was calculated at 294, 528 and 1024 µm respectively. With the best obtained parameters also butt-welding (BW) configuration was tested and it was possible to join two plates. In this second phase the influence of the material conditions was investigated and so both HR and SOL states were employed. The laser employed in this study was characterized by the properties listed in Table 2 . The parameters applied in this studied are listed in Table 3 , were the parameters variation tested in BoP study are highlighted. Table 2 Laser source characteristics Parameter Value Laser source IPG YLS 6000 C(T) Welding head IPG Wobble D50 Wavelength, λ 1070 nm Max laser power, 𝑃 𝑚𝑎𝑥 6 kW Fiber core, 𝑑 𝑓 100 µm Beam quality 11.2 Collimation length, 𝑓 𝑐 200 mm Focal length, 𝑓 𝑓 300 mm Waist diameter, 𝑑 0 150 µm Table 3 Laser beam welding parameters Fixed parameters Welding velocity, v 25 mm/s Shielding gas N 2 at 60 Nl/min Varied parameters Power, P 3.25 / 3.75 kW Focal position, Δz -2.5 / -5 / -10 mm Wobbling strategy None; Circular with A = 1.4 mm, f = 40 Hz From each weld, samples were obtained from different cross-sections. In this fashion, the consistency of the results along the whole weld track was verified. The cross-sections were analysed through Light Optical Microscope (LOM). Microstructural details were observed with Secondary Electron Microscope (SEM) and throw Energy Dispersive X-ray Spectroscopy (EDS) it was possible to compare local chemical compositions. Exploiting LOM images and ImageJ® software, dimensional measurements of the welds were performed. Exploiting SEM images and ImageJ® software it was possible to analyse microstructural features of smaller dimensions. The material hardness was characterized via Vickers microhardness tests (300g of load and 15s of dwell time). Measurements were taken on each cross-section along linear profiles with the aim to pass through FZ, HAZ and BM. The hardness profiles were correlated to a recognizable microstructural feature via ImageJ® software. The mechanical response of the welded material was analysed via tensile test. The tests were performed according to ASTM E8/E8M-21 on butt-welded material. Samples were obtained from the BW joined sheets via with water jet cutting technique to avoid undesired heating. After testing the fracture surfaces were analyses with SEM and EDS, to study the nature of the fracture mechanism and defects’ nature. Results Laser beam welding was performed in bead on plate and butt-welding configuration. Exploiting the possibilities given by autogenous welding in neither the condition filler material was utilized. The results are divided between bead on plate and butt-welding. In the first case, process parameters have been studied while in the second part these parameters have been applied to study the difference between the two material conditions studied. Process parameter selection with bead on plate tests Considering BoP test, different focus depth of the laser beam and different laser path were considered. To evaluate the welding quality was considered taking in account especially the porosity level and the welding pool shape. Cross-section of the different welds are reported in Fig. 2 . The variation of focus is reported, and it is between 2.5mm, 5 and 10mm below the top surface. It is possible to see that, irrespective of the parameter variation, welding quality is poor due to porosity presence and undesirable weld pool shape. In detail, a part of the typical keyhole shape, the weld pool profiles show depression on the top and surplus of material in the lower part. On the other hand, welds performed with circular are shown in Fig. 3 . In these images is possible a wider welding pool and reduced defects in its shape (i.e., depressions and expulsion of material). Porosity is also reduced but it is still present especially in case of 3.75 kW power. In addition, measurements on the different cross-section are reported in Table 4 . The focus variation didn’t change significantly the values reported except for measurements related to -10mm focus welding track. Such parameter choice has generated a greater weld area and a significantly higher amount of dendritic fraction. Both these values are caused by the much greater material surplus at the bottom of the plate: it provides a wider weld area value, and such material is characterized by cooling parameters promoting dendrite formation (also visible in the other cross-sections). A much wider weld width was provided by circular wobbling strategy. And among the circular wobbling it was possible to observe a higher dendritic fraction in the track performed with higher power. Table 4 Beam on plate tracks measurements Linear, Δz =-2.5 mm Weld area avg. [mm 2 ] Weld width avg. [mm] Dendrite fraction [%] 3.90 0.64 43% Linear, Δz =-5 mm 3.77 0.65 46% Linear, Δz =-10 mm 5.42 0.72 62% Circular wobbling, P = 3.75 kW, Δz =-2.5 mm 8.26 1.62 50% Circular wobbling, P = 3.25 kW, Δz =-2.5 mm 8.44 1.63 42% Irrespective of the technique used, the WZ is clearly visible and show dendritic microstructure with different reaction to the chemical etching: brighter in case of columnar grains, darker for equiaxed dendrites region. The fraction of this last region over the total welding area is reported in Table 4 . The HAZ is not visible via OM in Fig. 2 and Fig. 3 but it is visible at higher magnification in a SEM image (Fig. 4 ). Grain coarsened HAZ was detected only in the first row of grains adjacent to the weld track with a width of less than ~ 70 µm, while on the right side of the image, much smaller grains, that appear unaffected, are visible. Hardness profile was measured in each cross-section. In Fig. 5 , the hardness profile from the different test of BoP are represented. All of the profile show a decrease of hardness in the WZ. In the case of circular wobbling tests (here lebelled as Wobbling 3.75kW and Wobbling 3.25kW) the WZ is wider and as results the decrease of hardness is shown in a wider range while the other tracks show a narrower drop of hardness. In addiction, it is possbile to observe an increase of hardnening in the HAZ, for the linear bead test such hardness increase is redueced to only a minimum distance from the WZ, while for the circular wobbling such hardening appear to be present even further from the WZ. At the end of the analyses the welding condition with wobbling and laser power at 3.25 kW and focal point at -2.5 mm was chosen for further analyses. Influence of material condition prior to laser welding As in the case of BoP, four cross-sections from the butt-welding test were analysed and their results are reported in Fig. 6 . Similar shape of the welding pool and similar features in the WZ to circular wobbling BoP samples are visible and, also in this case, evident grain growth is not observable at the reported magnification. Also, in this case wide weld pool and partially columnar and dendritic structure is observed. Pores are evident especially in the HR condition and especially in the third cross-section a big pore is visible with almost 500 µm of diameter and in the second cross-section a narrow void is visible. In all the sections, lack of filler material during the operation caused irregularity in the weld pool shape and in all of them the weld pool had lower thickness than the base material. Such characteristic adds a geometrical inhomogeneity to a region already characterized by microstructural inhomogeneity and porosity presence, making such area the most likely weakest material region in the following mechanical test (i.e., uniaxial tensile test). As for BoP cross-sections, measurements on the cross-sections are reported in Table 5 . The HR sections are showing narrower weld tracks although the differences are very limited. On average, the SOL sections are showing a higher fraction of dendrites but the values are significantly scattered and so it is not considered reliable. Table 5 Butt-welding cross-section measurements Cross-section Weld Area avg. [mm 2 ] Weld width avg. [mm] Dendritic area [mm 2 ] Dendrite fraction [%] HR 1 7.34 1.52 2.62 36% 2 7.60 1.56 2.48 33% 3 6.84 1.53 1.00 15% 4 6.80 1.56 1.13 17% avg . 7.15 1.54 1.81 25% SOL 1 6.95 1.54 2.35 34% 2 7.90 1.58 2.16 27% 3 7.64 1.60 3.96 52% 4 7.39 1.55 1.86 25% avg. 7.47 1.57 2.58 35% In these cross-sections also the microhardness was measured and reported in Fig. 7 . Considering the results from HR samples, the BM values are significantly higher than WZ values, similar to what was observed in BoP tests. On the other hand, the results from SOL samples show only a minimal lower hardness difference between WZ and the furthest values (almost ~ 20 HV). In Fig. 7 , it is also possible to appreciate the effect of the thermal treatment on the material hardness: the SOL material’s hardness is reasonably lower. The mechanical response was studied throw uniaxial tensile tests. The specimen fractures have been observed in the center of the WZ in all the cases and the obtained results are shown in Fig. 8 , Fig. 9 and Fig. 10 . From the shown curves, it is clearly visible that HR samples have significant lower elongation than SOL samples. The lower tensile properties of LBW samples could be explained by the defects observed in the cross-sections as the change in thickness in the WZ and the presence of porosity. These behaved as a stress intensification factor so as weak point in the center of the tensile test specimen gauge length. Comparing the data to the one related to un-welded material [ 43 ], it is visible how this intensification factor has promoted and early fracture. Via surface fracture observation, it was confirmed that the lower performance of the HR samples is related to the significantly high amount of porosity, that was observed on the surface fracture as visible in Fig. 9 . The presence of big pores clearly reduced the resistance of the WZ during the tensile test and so it leaded to premature fracture of the samples. This study material usually shows a ductile fracture with significant presence of voids and dimples and not this excessive amount of porosity. Discussion Considering firstly the results obtained by bead on plate technique, the effect of focus depth variation is observed. The best results, especially in terms of weld pool geometry, was obtained with a focus depth of -2.5mm. In such weld track, excessive material in the bottom and lack on the top were limited. Although these good results, successive tests with circular wobbling were carried out showing even better results in terms of welding pool width, less weld shape issues (i.d., depression and excess of material) and, therefore, a better weld poll geometry. In the study of material hardness, different spikes of hardness were observed close to the weld pool. Such increase of hardness could be due to the internal stress present during solidification which could be generated by the missing feeding material that instead could mitigate such problem. In addition, also the microstructure could promote such higher hardness. Presence of very short dendrites close to the external part of the weld was noted while the central part the microstructure is mainly composed of big columnar grains. And in studies with different technique and materials is reported that smaller dendrites lead to higher hardness [ 44 , 45 ]. Although κ-carbides precipitation was expected and could be part of the hardness spikes’ reason, no clear signs of their presence were observed during the microstructure analysis. Considering the results obtained on the butt-welded samples, it was observed a microstructure very similar to the one observed in circular wobbling BoP tracks. A wide weld pool is able to promote the chemical homogenization and a lower amount of dendrite in comparison with BoP study. Also in the microhardness study, different results were observed according to the material condition: HR material showed a significant softening in the WZ, while for SOL material the softening was very limited and barely observable. Unfortunately, defects as misalignment and excessive porosity were observed. Some pores of little dimensions were observed in the SOL cross-sections, but in the HR ones such pores are much bigger, as visible in Fig. 6 , Fig. 9 and Fig. 10 . The presence of pores might be due to excessive evaporation of the material, especially Mn [ 26 ]. To evaluate such possibility, an EDS chemical analysis was performed close a pore (Fig. 11 ), also visible in cross-section of HR sample in Fig. 6 , along with the pore visible on the tensile test specimen fracture surface (Fig. 9 and Fig. 10 ). No significant change in composition or elemental enrichment/depletion was observed (as in the graphs reported in Fig. 11 ), so no significant evidence traces of specific element close to vaporization site was found. Although no clear evidence in the EDS was observed, the significant higher number of pores in the HR sample could be explained by Mn banding [ 46 ]. In the HR material, it was observed a slightly different concentration in Mn in form of bands parallel to the rolling direction. In the SOL samples chemical homogenization was promoted by the thermal treatment and less pores were observed. The BM inhomogeneity could reflect in different responses in the laser welding procedure, and it could be at the basis of the higher content of pores in the HR samples. Conclusion The weldability of a high-Mn austenitic lightweight steel was investigated by autogenous laser beam welding. Bead-on-plate tests demonstrated that a focal position of − 2.5 mm combined with a circular wobbling strategy improved weld pool geometry and reduced surface defects. The weld zone exhibited a mixed columnar–dendritic microstructure and an extremely narrow grain-coarsened HAZ. A hardness drop in the weld zone was observed in all conditions, being pronounced in the hot-rolled material and limited in the solubilized state. Butt-welded joints in the hot-rolled condition showed significant porosity, leading to premature failure during tensile testing. The solubilized material exhibited reduced porosity and superior mechanical performance. These results indicate that material condition and process stability are key factors for reliable laser welding of high-Mn lightweight steels. Declarations Competing interests The authors declare that they have no competing interests. Funding This work was supported by the Research Fund for Coal and Steel (grant agreement No. 899332) . Authors’ contributions Giacomo Villa : Conceptualization; Investigation; Validation; Writing – original draft, Silvia Barella : Conceptualization; Methodology; Supervision; Writing – review & editing, Davide Mombelli : Conceptualization; Methodology; Supervision; Writing – review & editing, Andrea Gruttadauria : Conceptualization, Carlo Mapelli : Conceptualization; Supervision; Funding acquisition, Shaad Ahmad : Investigation, Kenan Kaan Yetil : Investigation, Ali Gökhan Demir : Investigation; Writing – review & editing. 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Available from: https://www.tandfonline.com/doi/abs/ 10.1179/1362171813Y.0000000140 Zhao YY, Zhang YS, Hu W (2013) Effect of welding speed on microstructure, hardness and tensile properties in laser welding of advanced high strength steel. Sci Technol Weld Joining 18(7):581–590 Sreenivasan N, Xia M, Lawson S, Zhou Y (2008) Effect of laser welding on formability of DP980 steel. J Eng Mater Technol [Internet]. Oct 1 [cited 2024 Feb 13];130(4):0410041–9. Available from: https://dx.doi.org/10.1115/1.2969246 Pieters RRGM, Krasnoperov MY, Richardson IM Laser welding of high strength steels. ICALEO 2003–22nd International Congress on Applications of Laser and Electro-Optics, Congress Proceedings [Internet]. 2003 Oct 1 [cited 2024 Feb 13]; Available from: /lia/liacp/article/doi/10.2351/1.5060162/398368/Laser-welding-of-high-strength-steels Kuryntsev SV, Gilmutdinov AK The effect of laser beam wobbling mode in welding process for structural steels. International Journal of Advanced Manufacturing Technology [Internet]. 2015 Dec 1 [cited 2024 Nov 10];81(9–12):1683–91. Available from: https://link.springer.com/article/ 10.1007/s00170-015-7312-y Sanati S, Nabavi SF, Esmaili R, Farshidianfar A, Dalir H A Comprehensive Review of Laser Wobble Welding Processes in Metal Materials: Processing Parameters and Practical Applications. Lasers in Manufacturing and Materials Processing 2024 11:2 [Internet]. 2024 Feb 5 [cited 2024 Nov 10];11(2):492–528. Available from: https://link.springer.com/ article/10.1007/s40516-024-00245-w Kang M, Kim YM, Han HN, Kim C (2075) Effects of Phase Evolution on Mechanical Properties of Laser-Welded Ferritic Fe-Al-Mn-C Steel. Metals 2017, Vol 7, Page 523 [Internet]. 2017 Nov 24 [cited 2024 Feb 13];7(12):523. Available from: https://www.mdpi.com/ -4701/7/12/523/htm Gomez A, Banis A, Avella M, Molina-Aldareguia JM, Petrov RH, Dutta A et al (2024) The effect of κ-carbides on high cycle fatigue behavior of a Fe-Mn-Al-C lightweight steel. Int J Fatigue 184:108306 Sun J, Ren W, Nie P, Huang J, Zhang K, Li Z (2019) Study on the weldability, microstructure and mechanical properties of thick Inconel 617 plate using narrow gap laser welding method. Mater Des 175:107823 Yang J, Dong H, Xia Y, Li P, Ma Y, Wu W et al (2021) The microstructure and mechanical properties of novel cryogenic twinning-induced plasticity steel welded joint. Mater Sci Engineering: A 818:141449 Picak S, Vaughan MW, Atwani O, El, Mott A, Limmer KR, Karaman I (2023) Effects of chemical segregation on ductility-anisotropy in high strength Fe-Mn-Al-C lightweight austenitic steels. Acta Mater 245:118589 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 11 May, 2026 Reviewers invited by journal 06 May, 2026 Editor invited by journal 06 May, 2026 Editor assigned by journal 05 May, 2026 First submitted to journal 04 May, 2026 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-9573879","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":635635234,"identity":"de376a60-6b08-4642-8ce3-5a350e9f3b07","order_by":0,"name":"Giacomo Villa","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Giacomo","middleName":"","lastName":"Villa","suffix":""},{"id":635635235,"identity":"2b68c1ac-c95f-4b00-a399-000172ae5cb9","order_by":1,"name":"Silvia Barella","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIie3PMWrDMBTG8U8InCWgVVmaK6hbh9CzPBHI6MVLhxBcTJ0tOUCHXsFHeEGQyaRrSxZ16ZwpZAq1m7TpYptuheqPpod+6AkIhf5iUqYg1AeCPUZAT9QT3ULENwETJl8T3WKqC7gQV5HTvJEM5yLXfopYPTpmmj7HSsqHwuNm1kSMqwitkejNhJjW22SQifylbTEjRWYogk3LvmGKtrZwHWSY1eQI+1SqHdNx003gxL23OWxR9sE2525iPslCJ9dlZNguxue/GD1ImxZbOl4d9qP4qpRvfre/jVVv/v56uJupxsVOXbag8+sd4Gf0i7uhUCj0T/oA2kVboSDbRq4AAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-1866-6674","institution":"Politecnico di Milano","correspondingAuthor":true,"prefix":"","firstName":"Silvia","middleName":"","lastName":"Barella","suffix":""},{"id":635635236,"identity":"3c308753-ad8a-491e-a2ee-07f865b38356","order_by":2,"name":"Davide Mombelli","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Davide","middleName":"","lastName":"Mombelli","suffix":""},{"id":635635237,"identity":"d726635f-f2d8-4a85-aee2-6cd7f2ae7124","order_by":3,"name":"Andrea Gruttadauria","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Andrea","middleName":"","lastName":"Gruttadauria","suffix":""},{"id":635635238,"identity":"811a19ac-8f14-4213-bce5-05b76913ca55","order_by":4,"name":"Carlo Mapelli","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Carlo","middleName":"","lastName":"Mapelli","suffix":""},{"id":635635239,"identity":"0a269333-eab2-40db-b0af-89144e227776","order_by":5,"name":"Shaad Ahmad","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Shaad","middleName":"","lastName":"Ahmad","suffix":""},{"id":635635240,"identity":"363f4621-e7e5-4f60-b40d-9c6e2d56603f","order_by":6,"name":"Kenan Kaan Yetil","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Kenan","middleName":"Kaan","lastName":"Yetil","suffix":""},{"id":635635241,"identity":"d0be0e17-4ae4-4726-8a95-e9716d4cda1f","order_by":7,"name":"Ali Gökhan Demir","email":"","orcid":"","institution":"Politecnico di Milano","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"Gökhan","lastName":"Demir","suffix":""}],"badges":[],"createdAt":"2026-04-30 08:05:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9573879/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9573879/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109317185,"identity":"cfaeb09b-0061-438a-9cec-59adb2b3abb5","added_by":"auto","created_at":"2026-05-15 12:40:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":58442,"visible":true,"origin":"","legend":"\u003cp\u003escheme of operations\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/3a3d786e5e0c36b320eeeffd.png"},{"id":109317150,"identity":"022fa6c0-ae3c-4f01-9604-c6d4eb02b2a8","added_by":"auto","created_at":"2026-05-15 12:39:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1563164,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of focus variation with laser power of 3.25 kW on bead on plate track's microstructure. Images have been extracted from different cross-section\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/56528c52ad186c362d17b831.png"},{"id":109317210,"identity":"989843dc-bc14-4d50-b531-efa4963d49a6","added_by":"auto","created_at":"2026-05-15 12:40:04","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":862251,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of power variation with focal position of 2.5 mm on circular wobbling bead on plate track's microstructure. Images have been extracted from different cross-section\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/7ffa24b157091ef830a13a4a.png"},{"id":109317230,"identity":"5b1559a1-c07e-48c4-a317-2770d300a51b","added_by":"auto","created_at":"2026-05-15 12:40:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1031271,"visible":true,"origin":"","legend":"\u003cp\u003eSEM image of WZ, HAZ and BM of BoP sample.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/1a426de10a76c9cf30ddcb20.png"},{"id":109316926,"identity":"357b4b45-1de7-49c8-8960-c3b39bc7093a","added_by":"auto","created_at":"2026-05-15 12:39:28","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":163217,"visible":true,"origin":"","legend":"\u003cp\u003eHardness profile (middle thickness) for the different BoP tracks\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/c296cfc898f83b5b56416ded.png"},{"id":109317085,"identity":"497db776-009d-489f-b5b0-45e7964184e2","added_by":"auto","created_at":"2026-05-15 12:39:45","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1522274,"visible":true,"origin":"","legend":"\u003cp\u003eLaser butt welding, with laser power of 3.25kW and focal position of -2.5mm, cross-sections microstructure images from optical microscope\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/cf78ae7e49e7648838cc32c1.png"},{"id":109317148,"identity":"d5f4308e-f24a-4efd-8cc6-c343f6f63378","added_by":"auto","created_at":"2026-05-15 12:39:50","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":146931,"visible":true,"origin":"","legend":"\u003cp\u003eHardness profiles results for BW testing\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/71b73a6be597ff399961df8f.png"},{"id":109316924,"identity":"806a757e-f3ea-44f8-8859-6ba4e3d2ce36","added_by":"auto","created_at":"2026-05-15 12:39:28","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":84016,"visible":true,"origin":"","legend":"\u003cp\u003eLaser butt welding uniaxial tensile test results (BM data from [43]).\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/bfa97940da5342e6456f4fed.png"},{"id":109316992,"identity":"702f4af8-67ef-4ceb-829f-2f52897f92aa","added_by":"auto","created_at":"2026-05-15 12:39:37","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":362530,"visible":true,"origin":"","legend":"\u003cp\u003eLaser but welding uniaxial HR tensile test specimen fracture surfaces\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/2e24b9ab4c6ff5e5e178ac91.png"},{"id":109316952,"identity":"6d8bb481-3d16-4338-adc0-e80ab076f1ac","added_by":"auto","created_at":"2026-05-15 12:39:30","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":323806,"visible":true,"origin":"","legend":"\u003cp\u003eLaser but welding uniaxial SOL tensile test specimen fracture surfaces\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/a05768fc5435b13b055aa0a8.png"},{"id":109316922,"identity":"11bfb9b6-a587-4761-a62c-ddc9872c1f2c","added_by":"auto","created_at":"2026-05-15 12:39:28","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":669347,"visible":true,"origin":"","legend":"\u003cp\u003eEDS analysis close to pore in cross-section (above) and on fracture surface (below)\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/1c9239c10d8b789599c88957.png"},{"id":109405284,"identity":"8b921a71-5868-4158-b172-6e0c497d9789","added_by":"auto","created_at":"2026-05-17 13:16:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7937477,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9573879/v1/07f997f2-b277-406a-9044-458adb6e6bf7.pdf"}],"financialInterests":"","formattedTitle":"Autogenous laser welding of high Mn lightweight steel for automotive applications","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMany sectors are pushing toward a reduction of emissions and energy consumption and, especially in transport, weight reduction is fundamental to achieve considerable energy savings [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eClassically weigh reduction is obtain by means of lower density alloys (e.g., Al) or the use of alloys with higher strength (e.g., Ultra-High Strength Steel) [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In both cases pros and cons are to be considered such as more energy consuming production and difficulties in the joining for Al [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and excessive thickness reduction in case of UHSS.\u003c/p\u003e \u003cp\u003eThe pros of lighter material and higher strength could be combined in innovative lightweight steels alloys.\u003c/p\u003e \u003cp\u003eSuch alloys are featured by low density (10% lower than high strength steels, 15% lower than Hadfield steels and AISI 304, and 16% lower than AISI 316) and high mechanical strength (up to 1500MPa ultimate tensile stress -UTS- and 80% elongation at break) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSuch properties are obtained balancing between the main alloying elements: Mn, Al, and C. They point out ferritic, austenitic, or duplex microstructure featured by different properties [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The austenitic microstructure is obtained by Al concentration of ~\u0026thinsp;5\u0026ndash;12%, Mn of ~\u0026thinsp;12\u0026ndash;30% and C of ~\u0026thinsp;0.6-2% and they have UTS of ~\u0026thinsp;800\u0026ndash;1500 MPa and TE of ~\u0026thinsp;30\u0026ndash;80% [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese alloys\u0026rsquo; most studied strengthening method is κ-carbides precipitation. Such carbides are featured by an E2\u003csub\u003e1\u003c/sub\u003e structure with a stoichiometric formula of (Fe,Mn)\u003csub\u003e3\u003c/sub\u003eAlC. In austenitic steels they can be intra-granular κ\u0026rsquo; finely dispersed in the austenitic matrix, improving the mechanical properties, or they can be inter-granular κ*, as a second phase at grain boundaries having detrimental effects [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConsidering the future application in automotive applications, it is of the upmost importance the weldability of these alloys. Some criticalities are expected due to the richness of the chemical composition and the material\u0026rsquo;s susceptibility to unwanted thermal treatments\u0026rsquo; effects. Grain coarsening has been observed [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], but the most detrimental is undesired phases presence, as ferrite [\u003cspan additionalcitationids=\"CR17 CR18 CR19\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], κ-carbides [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and b-Mn [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. In addition, possible Mn evaporation during the melting procedure can be observed [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Due to material microstructure (fully austenitic) hot cracks in the weld metal and distortion of the workpiece may be observed [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eArc welding requires filler material to fill the root gap and to control the welds quality. In case of heterogeneous filler, it requires a deep research and investigation, and, in case of homogenous material, it requires to be manufactured in precise dimensions and in case of material still in research phase it might be difficult to shape the material accordingly [\u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Such necessities could be avoided via autogenous welding.\u003c/p\u003e \u003cp\u003eLaser beam welding (LBW) could perform such type of welding [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], avoiding so time-consuming and costly development of filler material or manufactory of homogenous filler. This technology has become a pivotal technology in the automotive sector, particularly due to its precision, efficiency, and ability to handle advanced high-strength steels (AHSS). This technology is used in the automotive industry for body-in-white (BIW) assembly, including body frames, door frames, trunks, auto hoods, and chassis [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. It is highly versatile, capable of welding various materials and thicknesses, and it is used for different joint types, such as butt joints, lap joints, and tailored blanks and it could be performed without contact. LBW systems are also highly compatible with automated production lines, enhancing efficiency and consistency in mass production [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLaser welding is particularly effective with high-strength materials, like AHSS, due to its ability to create strong joints with minimal heat-affected zones (HAZ) and extremely localized energy delivery, preserving the material properties [\u003cspan additionalcitationids=\"CR37 CR38\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDue to the possibilities given from laser automatization it is also possible to modify the laser beam path leading to wobbling strategies that can be beneficial in porosity reduction, microstructural control and, especially in case of autogenous welding, in gap bridging [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough lightweight steels weldability is a topic of the upmost importance, limited studies have been presented and even less studies focused on laser beam welding technique [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. In this study the weldability of a high Mn austenitic lightweight steel alloy has been investigated via laser beam welding. Different welding configuration (beam on plate and butt-welding) have been performed and different material conditions (as hot rolled and after solubilization) have been employed. The welded zone morphology and microhardness have been studied along with tensile properties of the welded material.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eIn this study, weldability of an austenitic lightweight steel was investigated. The nominal composition and the one obtained by OES (optical emission spectroscopy) is reported in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This material density was measured to be almost 6.7 g/cm\u003csup\u003e3\u003c/sup\u003e, so significantly lower than other commercial austenitic steels like AISI 304 or 316 (8 g/cm\u003csup\u003e3\u003c/sup\u003e) and Hadfield steels (7.890 g/cm\u003csup\u003e3\u003c/sup\u003e).\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\u003eOES and nominal chemical composition\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ewt.%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOES\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e59.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNominal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe material was studied in two conditions: hot rolled (labelled HR) and after solubilization, performed at 1000\u0026deg;C with holding time of 30min, (labelled SOL). The material was in the form of 5 mm thick plates for both conditions.\u003c/p\u003e \u003cp\u003eTwo different welding configurations were tested in this study performed via automatized LBW (as in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). An initial test was performed with bead on plate (BoP) configuration to study the material response to LBW. In this part of the study the welding parameters was modified to reach satisfactory results in terms of weld seam geometry and hardness distribution. In this part of the study, only HR material was employed. In particular, laser welding with a stationary beam was compared to a wobbling weld with a circular trajectory. Laser power was varied in a relatively restricted region between 3.25 and 3.5 kW according to the results of preliminary tests not described here for brevity. The focal position was varied at -2.5, 5, and \u0026minus;\u0026thinsp;10 mm in order to employ larger spot diameters on the material surface, hence enlarging the melt pool. At these focal positions, the laser beam diameter was calculated at 294, 528 and 1024 \u0026micro;m respectively.\u003c/p\u003e \u003cp\u003eWith the best obtained parameters also butt-welding (BW) configuration was tested and it was possible to join two plates. In this second phase the influence of the material conditions was investigated and so both HR and SOL states were employed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe laser employed in this study was characterized by the properties listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The parameters applied in this studied are listed in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, were the parameters variation tested in BoP study are highlighted.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLaser source characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLaser source\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIPG YLS 6000 C(T)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWelding head\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIPG Wobble D50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWavelength, λ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1070 nm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMax laser power, \u0026#119875;\u003csub\u003e\u0026#119898;\u0026#119886;\u0026#119909;\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 kW\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFiber core, \u0026#119889;\u003csub\u003e\u0026#119891;\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100 \u0026micro;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBeam quality\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCollimation length, \u0026#119891;\u003csub\u003e\u0026#119888;\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFocal length, \u0026#119891;\u003csub\u003e\u0026#119891;\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e300 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWaist diameter, \u0026#119889;\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e150 \u0026micro;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLaser beam welding parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eFixed parameters\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWelding velocity, v\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25 mm/s\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShielding gas\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003csub\u003e2\u003c/sub\u003e at 60 Nl/min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVaried parameters\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePower, P\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.25 / 3.75 kW\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFocal position, Δz\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-2.5 / -5 / -10 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWobbling strategy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNone; Circular with A\u0026thinsp;=\u0026thinsp;1.4 mm, f\u0026thinsp;=\u0026thinsp;40 Hz\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFrom each weld, samples were obtained from different cross-sections. In this fashion, the consistency of the results along the whole weld track was verified.\u003c/p\u003e \u003cp\u003eThe cross-sections were analysed through Light Optical Microscope (LOM). Microstructural details were observed with Secondary Electron Microscope (SEM) and throw Energy Dispersive X-ray Spectroscopy (EDS) it was possible to compare local chemical compositions. Exploiting LOM images and ImageJ\u0026reg; software, dimensional measurements of the welds were performed. Exploiting SEM images and ImageJ\u0026reg; software it was possible to analyse microstructural features of smaller dimensions.\u003c/p\u003e \u003cp\u003eThe material hardness was characterized via Vickers microhardness tests (300g of load and 15s of dwell time). Measurements were taken on each cross-section along linear profiles with the aim to pass through FZ, HAZ and BM. The hardness profiles were correlated to a recognizable microstructural feature via ImageJ\u0026reg; software.\u003c/p\u003e \u003cp\u003eThe mechanical response of the welded material was analysed via tensile test. The tests were performed according to ASTM E8/E8M-21 on butt-welded material. Samples were obtained from the BW joined sheets via with water jet cutting technique to avoid undesired heating.\u003c/p\u003e \u003cp\u003eAfter testing the fracture surfaces were analyses with SEM and EDS, to study the nature of the fracture mechanism and defects\u0026rsquo; nature.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eLaser beam welding was performed in bead on plate and butt-welding configuration. Exploiting the possibilities given by autogenous welding in neither the condition filler material was utilized. The results are divided between bead on plate and butt-welding. In the first case, process parameters have been studied while in the second part these parameters have been applied to study the difference between the two material conditions studied.\u003c/p\u003e\n\u003ch3\u003eProcess parameter selection with bead on plate tests\u003c/h3\u003e\n\u003cp\u003eConsidering BoP test, different focus depth of the laser beam and different laser path were considered. To evaluate the welding quality was considered taking in account especially the porosity level and the welding pool shape. Cross-section of the different welds are reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The variation of focus is reported, and it is between 2.5mm, 5 and 10mm below the top surface. It is possible to see that, irrespective of the parameter variation, welding quality is poor due to porosity presence and undesirable weld pool shape. In detail, a part of the typical keyhole shape, the weld pool profiles show depression on the top and surplus of material in the lower part. On the other hand, welds performed with circular are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In these images is possible a wider welding pool and reduced defects in its shape (i.e., depressions and expulsion of material). Porosity is also reduced but it is still present especially in case of 3.75 kW power.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition, measurements on the different cross-section are reported in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The focus variation didn\u0026rsquo;t change significantly the values reported except for measurements related to -10mm focus welding track. Such parameter choice has generated a greater weld area and a significantly higher amount of dendritic fraction. Both these values are caused by the much greater material surplus at the bottom of the plate: it provides a wider weld area value, and such material is characterized by cooling parameters promoting dendrite formation (also visible in the other cross-sections). A much wider weld width was provided by circular wobbling strategy. And among the circular wobbling it was possible to observe a higher dendritic fraction in the track performed with higher power.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBeam on plate tracks measurements\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLinear, Δz =-2.5 mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWeld area avg. [mm\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeld width avg. [mm]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDendrite fraction [%]\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.90\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.64\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLinear, Δz =-5 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e46%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLinear, Δz =-10 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e62%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCircular wobbling, P\u0026thinsp;=\u0026thinsp;3.75 kW, Δz =-2.5 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCircular wobbling, P\u0026thinsp;=\u0026thinsp;3.25 kW, Δz =-2.5 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIrrespective of the technique used, the WZ is clearly visible and show dendritic microstructure with different reaction to the chemical etching: brighter in case of columnar grains, darker for equiaxed dendrites region. The fraction of this last region over the total welding area is reported in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe HAZ is not visible via OM in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e but it is visible at higher magnification in a SEM image (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Grain coarsened HAZ was detected only in the first row of grains adjacent to the weld track with a width of less than ~\u0026thinsp;70 \u0026micro;m, while on the right side of the image, much smaller grains, that appear unaffected, are visible.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHardness profile was measured in each cross-section. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the hardness profile from the different test of BoP are represented. All of the profile show a decrease of hardness in the WZ. In the case of circular wobbling tests (here lebelled as Wobbling 3.75kW and Wobbling 3.25kW) the WZ is wider and as results the decrease of hardness is shown in a wider range while the other tracks show a narrower drop of hardness. In addiction, it is possbile to observe an increase of hardnening in the HAZ, for the linear bead test such hardness increase is redueced to only a minimum distance from the WZ, while for the circular wobbling such hardening appear to be present even further from the WZ.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt the end of the analyses the welding condition with wobbling and laser power at 3.25 kW and focal point at -2.5 mm was chosen for further analyses.\u003c/p\u003e\n\u003ch3\u003eInfluence of material condition prior to laser welding\u003c/h3\u003e\n\u003cp\u003eAs in the case of BoP, four cross-sections from the butt-welding test were analysed and their results are reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Similar shape of the welding pool and similar features in the WZ to circular wobbling BoP samples are visible and, also in this case, evident grain growth is not observable at the reported magnification. Also, in this case wide weld pool and partially columnar and dendritic structure is observed.\u003c/p\u003e \u003cp\u003ePores are evident especially in the HR condition and especially in the third cross-section a big pore is visible with almost 500 \u0026micro;m of diameter and in the second cross-section a narrow void is visible.\u003c/p\u003e \u003cp\u003eIn all the sections, lack of filler material during the operation caused irregularity in the weld pool shape and in all of them the weld pool had lower thickness than the base material. Such characteristic adds a geometrical inhomogeneity to a region already characterized by microstructural inhomogeneity and porosity presence, making such area the most likely weakest material region in the following mechanical test (i.e., uniaxial tensile test).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs for BoP cross-sections, measurements on the cross-sections are reported in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The HR sections are showing narrower weld tracks although the differences are very limited. On average, the SOL sections are showing a higher fraction of dendrites but the values are significantly scattered and so it is not considered reliable.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eButt-welding cross-section measurements\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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 \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCross-section\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeld Area avg. [mm\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWeld width avg. [mm]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDendritic area [mm\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eDendrite fraction [%]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eHR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e36%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e33%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eavg\u003c/em\u003e.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e7.15\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003e1.54\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003e1.81\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003e25%\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eSOL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e34%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e52%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e25%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eavg.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e7.47\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003e1.57\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003e2.58\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003e35%\u003c/em\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 \u003cp\u003eIn these cross-sections also the microhardness was measured and reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eConsidering the results from HR samples, the BM values are significantly higher than WZ values, similar to what was observed in BoP tests. On the other hand, the results from SOL samples show only a minimal lower hardness difference between WZ and the furthest values (almost\u0026thinsp;~\u0026thinsp;20 HV). In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, it is also possible to appreciate the effect of the thermal treatment on the material hardness: the SOL material\u0026rsquo;s hardness is reasonably lower.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mechanical response was studied throw uniaxial tensile tests. The specimen fractures have been observed in the center of the WZ in all the cases and the obtained results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. From the shown curves, it is clearly visible that HR samples have significant lower elongation than SOL samples.\u003c/p\u003e \u003cp\u003eThe lower tensile properties of LBW samples could be explained by the defects observed in the cross-sections as the change in thickness in the WZ and the presence of porosity. These behaved as a stress intensification factor so as weak point in the center of the tensile test specimen gauge length.\u003c/p\u003e \u003cp\u003eComparing the data to the one related to un-welded material [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], it is visible how this intensification factor has promoted and early fracture.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eVia surface fracture observation, it was confirmed that the lower performance of the HR samples is related to the significantly high amount of porosity, that was observed on the surface fracture as visible in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The presence of big pores clearly reduced the resistance of the WZ during the tensile test and so it leaded to premature fracture of the samples.\u003c/p\u003e \u003cp\u003eThis study material usually shows a ductile fracture with significant presence of voids and dimples and not this excessive amount of porosity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eConsidering firstly the results obtained by bead on plate technique, the effect of focus depth variation is observed. The best results, especially in terms of weld pool geometry, was obtained with a focus depth of -2.5mm. In such weld track, excessive material in the bottom and lack on the top were limited. Although these good results, successive tests with circular wobbling were carried out showing even better results in terms of welding pool width, less weld shape issues (i.d., depression and excess of material) and, therefore, a better weld poll geometry.\u003c/p\u003e \u003cp\u003eIn the study of material hardness, different spikes of hardness were observed close to the weld pool. Such increase of hardness could be due to the internal stress present during solidification which could be generated by the missing feeding material that instead could mitigate such problem. In addition, also the microstructure could promote such higher hardness. Presence of very short dendrites close to the external part of the weld was noted while the central part the microstructure is mainly composed of big columnar grains. And in studies with different technique and materials is reported that smaller dendrites lead to higher hardness [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Although κ-carbides precipitation was expected and could be part of the hardness spikes\u0026rsquo; reason, no clear signs of their presence were observed during the microstructure analysis.\u003c/p\u003e \u003cp\u003eConsidering the results obtained on the butt-welded samples, it was observed a microstructure very similar to the one observed in circular wobbling BoP tracks. A wide weld pool is able to promote the chemical homogenization and a lower amount of dendrite in comparison with BoP study. Also in the microhardness study, different results were observed according to the material condition: HR material showed a significant softening in the WZ, while for SOL material the softening was very limited and barely observable.\u003c/p\u003e \u003cp\u003eUnfortunately, defects as misalignment and excessive porosity were observed. Some pores of little dimensions were observed in the SOL cross-sections, but in the HR ones such pores are much bigger, as visible in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe presence of pores might be due to excessive evaporation of the material, especially Mn [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. To evaluate such possibility, an EDS chemical analysis was performed close a pore (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e), also visible in cross-section of HR sample in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, along with the pore visible on the tensile test specimen fracture surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). No significant change in composition or elemental enrichment/depletion was observed (as in the graphs reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e), so no significant evidence traces of specific element close to vaporization site was found.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAlthough no clear evidence in the EDS was observed, the significant higher number of pores in the HR sample could be explained by Mn banding [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. In the HR material, it was observed a slightly different concentration in Mn in form of bands parallel to the rolling direction. In the SOL samples chemical homogenization was promoted by the thermal treatment and less pores were observed.\u003c/p\u003e \u003cp\u003eThe BM inhomogeneity could reflect in different responses in the laser welding procedure, and it could be at the basis of the higher content of pores in the HR samples.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe weldability of a high-Mn austenitic lightweight steel was investigated by autogenous laser beam welding. Bead-on-plate tests demonstrated that a focal position of \u0026minus;\u0026thinsp;2.5 mm combined with a circular wobbling strategy improved weld pool geometry and reduced surface defects. The weld zone exhibited a mixed columnar\u0026ndash;dendritic microstructure and an extremely narrow grain-coarsened HAZ. A hardness drop in the weld zone was observed in all conditions, being pronounced in the hot-rolled material and limited in the solubilized state. Butt-welded joints in the hot-rolled condition showed significant porosity, leading to premature failure during tensile testing. The solubilized material exhibited reduced porosity and superior mechanical performance. These results indicate that material condition and process stability are key factors for reliable laser welding of high-Mn lightweight steels.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the \u003cb\u003eResearch Fund for Coal and Steel (grant agreement No. 899332)\u003c/b\u003e.\u003c/p\u003e\u003ch2\u003eAuthors\u0026rsquo; contributions\u003c/h2\u003e \u003cp\u003e \u003cb\u003eGiacomo Villa\u003c/b\u003e: Conceptualization; Investigation; Validation; Writing \u0026ndash; original draft, \u003cb\u003eSilvia Barella\u003c/b\u003e: Conceptualization; Methodology; Supervision; Writing \u0026ndash; review \u0026amp; editing, \u003cb\u003eDavide Mombelli\u003c/b\u003e: Conceptualization; Methodology; Supervision; Writing \u0026ndash; review \u0026amp; editing, \u003cb\u003eAndrea Gruttadauria\u003c/b\u003e: Conceptualization, \u003cb\u003eCarlo Mapelli\u003c/b\u003e: Conceptualization; Supervision; Funding acquisition, \u003cb\u003eShaad Ahmad\u003c/b\u003e: Investigation, \u003cb\u003eKenan Kaan Yetil\u003c/b\u003e: Investigation, \u003cb\u003eAli G\u0026ouml;khan Demir\u003c/b\u003e: Investigation; Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHelms H, Lambrecht UL, The International Journal of Life Cycle Assessment (2007) The potential contribution of light-weighting to reduce transport energy consumption [Internet]. 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Acta Mater 245:118589\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Welding, Light steel, laser","lastPublishedDoi":"10.21203/rs.3.rs-9573879/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9573879/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLightweight steels are an innovative steel grade whose research is very interesting for application in automotive sector. They are featured by high Mn and Al content, high mechanical properties (up to 800MPa of yield strength and up to 55% of elongation at break) and low density (13% lower than conventional stainless steel). Especially because of the application sector, the assessment of these alloys weldability is of outmost importance.\u003c/p\u003e \u003cp\u003eDue to the high content chemical elements different criticalities are expected, as Mn evaporation and κ-carbides precipitation. The former may lead to inhomogeneous chemical composition and so different microstructure, mechanical properties and difference response to welding process. The latter is the most studied strengthening method in this class of steel, but it may lead to excessive ductility loss.\u003c/p\u003e \u003cp\u003eAn austenitic with high Mn lightweight steel alloy has been tested with Laser Beam Welding with different configurations and different material conditions. Microstructure and mechanical properties of the welded joints has been investigated. Solid welded joints were obtained, but significant macro-porosity was observed in the hot rolled material. In the WZ, both a dendritic and columnar microstructure has been observed, while an extremely narrow grain coarsened-HAZ have been detected. In the WZ a limited softening has been observed in the material after solubilization while in the hot rolled one, the difference is more marked.\u003c/p\u003e \u003cp\u003eUniaxial tensile test has highlighted the macro-porosity effect in the HR samples while it has provided good results in the SOL samples.\u003c/p\u003e","manuscriptTitle":"Autogenous laser welding of high Mn lightweight steel for automotive applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-15 12:38:26","doi":"10.21203/rs.3.rs-9573879/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-05-11T07:52:59+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-06T15:33:56+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2026-05-06T11:06:52+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-05T14:09:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2026-05-04T05:16:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"70eda264-fc34-42cd-9a75-7e3f2039496c","owner":[],"postedDate":"May 15th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"","date":"2026-05-11T07:52:59+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-06T15:33:56+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2026-05-06T11:06:52+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-05T14:09:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2026-05-04T05:16:33+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-15T12:38:27+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-15 12:38:26","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9573879","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9573879","identity":"rs-9573879","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}