Grain size effect on the mechanical properties of C7701/Ti/C7701 ultra-thin composite foils by influencing element diffusion

Grain size effect on the mechanical properties of C7701/Ti/C7701 ultra-thin composite foils by influencing element diffusion | 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 Grain size effect on the mechanical properties of C7701/Ti/C7701 ultra-thin composite foils by influencing element diffusion Rui Chen, Zhihe Dou, Honemei Zhang, Tingan Zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6273194/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract With the increasing application of titanium and copper alloy materials and various sandwich composites in various precision machining fields, it has become increasingly important to study the complex changes in the internal microstructure of sandwich composites and their influencing factors during the microforming process. In this study, titanium and C7701 foils were heat-treated at different temperatures to obtain raw materials with different grain sizes and microstructures. The heat-treated foils were rolled into a sandwich structure in a C7701 / Ti / C7701 arrangement and the composite foil was annealed at the same temperature. Metallographic and SEM tests on the composite foils showed that the titanium and C7701 rolled laminates were well bonded at 400℃ and 500℃ before rolling, and there was a certain gradient of elemental diffusion in the bonded layer, and the XRD test showed that a variety of intermetallic compounds were produced in the bonded layer. By analyzing the element diffusion and intermetallic compound generation at the interface of composite foils and conducting microtensile mechanical property tests on composite foils, it is found that the grain size before rolling the composite has an important influence on the interfacial bonding and element diffusion of composite foils, which in turn affects the mechanical properties of composite foils. Micro forming composite foil Size effect Sandwich structure Mechanical property Figures Figure 1 Figure 2 Figure 3 Figure 4 1.Introduction Microforming technology is a technique suitable for the production of extremely small metal parts with clear economic and ecological advantages in many industrial product applications. The fundamental challenge in microforming systems stems from the pronounced size effect phenomenon, which manifests dual influences on both localized deformation mechanisms and global process stability. Addressing this technological barrier necessitates an integrated multidisciplinary framework that synthesizes advancements from electronic control systems, precision mechanical engineering, physical modeling techniques, surface chemistry interactions, and advanced material characterization methodologies [ 1 ]. Sandwich structures are more efficient than conventional designs of longitudinal stiffeners and stabilizing ring structures using a double-layer structure with an intermediate stabilizing medium. Sandwich structures are favored because of their higher flexural stiffness to weight ratio, lower transverse deformation, and higher yield resistance [ 2 , 3 ]. The production of sandwich materials mainly utilizes rolled composite technology, and the bonding interface will inevitably generate diffusion layers and a variety of intermetallic compounds during the production process, which have an important impact on the performance of sandwich materials.[ 4 – 8 ] Meanwhile, the multilayer rolling composite technology can further promote the grain refinement of the sandwich material. Jiang et al. [ 9 ] successfully prepared bulk Ti/Cu composites by ARB process and found that multilayer composite rolling can achieve grain refinement. Zhang et al. [ 10 ] prepared Ti/Ni multilayer composite plate materials by ARB method using industrial pure Ti and pure Ni plates as initial materials. With the increase of rolling passes, the microstructure refinement of Ti and Ni layers in the composites was obvious and the degree of uniformity was improved. The grain refinement and intermetallic compounds generated in the interlayer have a significant effect on the mechanical properties of composite plates. Imayev et al. [ 11 ] found that the effect of intermetallic compounds on the mechanical properties of the material is affected by the size of the grain size, and the reduction of grain size and increase in grain boundary area resulted in the Ti3Al intermetallic compounds reducing the formation of voids during the flow process. Lacaille et al. [ 12 ] found that the refinement of the grain size enhances the diffusional properties of the material because of the increase in the density of the grain boundaries, which in turn increases the macroscopic diffusivity. The grain boundaries are fast diffusion channels in the material. Liu et al. [ 13 ] found that the local strain in small-sized materials is dependent on the grain size and is heterogeneous across different grain sizes. As the macroscopic strain increases, the effect of grain size on the local strain increases and the difference in local strain between different grains becomes more pronounced. Most of the studies on sandwich structures focus on the preparation methods and performance characterization of conventional sizes, while there are fewer studies on the effects of grain size effects on the rolled composite behavior and performance of sandwich structures under ultra-thin composite foils. In this study, the micro-rolled composite behavior of two metal foils, the generation of intermetallic compounds in the bond layer of composite foils were analyzed in combination with the micro-rolled composite technology, and the mechanical properties of composite foils under the influence of a variety of complex factors were investigated. The influence of grain size effect on the mechanical properties of composite foils by affecting the microstructure of the composite foil bonding layer is investigated. 2.Equipment and methods 2.1 Equipment The GR-TF60/18 heat treatment furnace from China was selected for the heat treatment of titanium foil. For tensile testing, the XK-207s microtensile machine from China was used. The KEYENCE VHX-5000 Super Depth of Field Microscope from Japan was used for metallographic analysis. The S7-300 four-roll mill from China was used for rolling compound. Zeiss Sigma 300 scanning electron microscope from Germany was selected for SEM inspection. 2.2 Experimental methods The raw material for the heat treatment is pure titanium foil and C7701 foil with a thickness of 0.05 mm, a length of 80 mm and a width of 10 mm. Annealing was carried out in argon gas at temperatures of 400, 500 and 600°C, respectively, with a holding time of 1h, to obtain foils with different grain sizes and microstructures. The annealing process is carried out in a sealed environment, after the end of the insulation, pass into the room temperature argon gas flow as a cooling medium, to isolate the oxygen penetration at the same time to ensure the cooling efficiency. Titanium foils and C7701 foils annealed at different temperatures were subjected to metallographic observation to analyze the difference in microstructure at different temperatures, and the grain size of pure titanium foils annealed at different temperatures. Titanium foils and C7701 foils with the same annealing temperature were used as a group as the raw material for rolling, and were divided into 3 groups. Each group was stacked and combined in an arrangement of C7701/Ti/C7701 and rolled for lamination at a rolling force of 800N. After rolling, the composite foils were uniformly annealed at 600°C for the second annealing to ensure good diffusion of the interface layer. XRD analysis of the composite foil was carried out in the detection range of 20°-100° for 2 min to further determine the internal structure and organizational transformation of composite foil. Metallographic and SEM tests were carried out on the annealed composite foils to determine the rolling bond quality and elemental distribution. Microtensile tests were carried out on the composite foils at a crosshead speed of 0.1 mm/min to analyze the mechanical properties of the foils and the effects of grain size before rolling and microstructure after rolling on the mechanical properties. The experimental flow is shown in Fig. 1 . 3.Results and discussion As can be seen from Fig. 2 (1-6), the microstructure of C7701 foil annealed at 400°C retains grains distributed along the rolling direction, and the theoretical recrystallization temperature of C7701 is 483°C. It is obvious that C7701 foil fails to recrystallize at 400°C, and single equiaxed grains are generated in C7701 foil annealed at 500°C and 600°C, and the grain size increases with the increase of the annealing temperature. The grain sizes were calculated to be 7.1 μm (500°C) and 17.3 μm (600°C), respectively. The grain size of pure titanium increases with increasing annealing temperature. The grain sizes were 6.4 μm (400 ℃), 7.5 μm (500 ℃) and 16.7 μm (600 ℃), respectively. The titanium foil annealed at 600 ℃ produced needle-like β-phases at the grain boundaries. The theoretical phase transition temperature of pure titanium is 882 ℃, but the material size, cooling rate, annealing atmosphere and other factors affect the actual phase transition temperature of pure titanium. The smaller material size represents a smaller number of grains, a larger surface area, an increase in the proportion of surface atoms, and a higher surface energy, which reduces the phase transformation temperature [14,15]. Due to the grain size effect, the reduction in the number of grains leads to a consequent reduction in the number of grain boundaries, which reduces the hindrance to dislocation motion and the energy required for phase transformation, thus further reducing the phase transformation temperature. During the annealing process, argon was used as a protective atmosphere for annealing in a confined space, and a room temperature argon gas stream was introduced for cooling at the end of the holding period, which ensured the cooling efficiency and insulated the infiltration of oxygen. The possibility of oxygen dissolution into the pure titanium lattice was further prevented and lattice distortion was reduced, resulting in the generation of the β-phase at lower temperatures [16]. At the same time, due to the extremely low thickness of the material, the heat dissipation efficiency is further improved and the cooling rate is accelerated, which is conducive to the retention of the β-phase organization. Under the combined influence of these factors, the generation of the β-phase at a lower temperature than the theoretical phase transition temperature was finally realized. From Fig. 2 (7-12), it can be seen that the composite foil in the polished state has no obvious cracking, and there exists a clear demarcation line between C7701 and Ti. For the composite foil at 600 ℃ before rolling, the jagged structure at the interface is more obvious, which is due to the larger grain size at 600 ℃, and the intensification of the grain ruler effect leads to uneven deformation, which produces a jagged bonding interface. After corrosion of the sample bonding interface color is darker, this is due to the process of heat treatment of the two materials elements diffuse each other to form a variety of elements mixed bonding layer, and at the same time by the two corrosive agents and darker color. Fig 2 (13-15) shows the backscattering pictures of the composite foil, which can clearly show that there is an obvious elemental lining at the interface, which further confirms that the elements of the two materials diffuse into each other during heat treatment, and at the same time, it can be seen that at higher multiplicity, the samples at 600°C before rolling are affected by the grain size effect, and there is an obvious rupture at the interface. According to the position of the asterisk in Fig. 3 (1-3), elemental point scanning is carried out at the interface of the composite foil, elemental line scanning is carried out perpendicular to the direction of the interface according to the position of the yellow line, and surface scanning is carried out to analyze the composite foil. Fig. 3 (4-6) shows that the elemental diffusion of the composite foil is not a cliff-like decline, proving that there is a certain gradient of elemental diffusion. The line scan results show that the Cu and Ni elements show a tendency of rising and then falling at the interface, and the surface scan results in Fig. 3 (10-12) show that the Cu and Ni elements have obvious aggregation phenomenon in the interfacial layer, whereas the point scan results in Fig. 3 (7-9) show that the Zn element exists less at the interface, which is almost negligible, and is mainly dominated by the Ti, Cu and Ni elements. Compared with the single-layer foil, the grain size of the composite foil is significantly reduced and an element diffusion layer is formed at the interface. Affected by the physical form of the sandwich structure, the growth of grains is limited by the space, so that the grain size of the composite foil is smaller, and at the same time by the grain size effect, the interface part of the rolling process due to uneven distribution of grains will produce a random distribution of stress concentration, and in the annealing process after rolling by the influence of the interface effect, the interface of the stress concentration at the interface will promote the nucleation of the new grains, further limiting the growth of the grains. The high temperature environment during the annealing process provides sufficient energy for metal atoms to migrate near the interface. This migration allows atoms originally present in each material to cross the interface into the other material, where elemental diffusion occurs. As shown in Fig. 3 (13), XRD examination of the samples, combined with the Ti-Cu, Ti-Ni, Ti-Zn binary phase diagrams [17-19] and EDS point-scan mass ratios, as well as the heat treatment process, it can be determined that intermetallic compounds dominated by Ti2Cu and Ti2Ni have been generated at the interface. Different intermetallic compounds have different effects on the material properties, in this paper, the diffusion and binding of elements basically occurs in the elemental diffusion layer between the two foil layers, which indicates that the distribution of intermetallic compounds is strictly limited to the diffusion layer part. The mixing of intermetallic compounds with different properties in a smaller space further cuts the elemental distribution of the composite foil. As shown in Fig. 4 (1-3), the mechanical properties of the composite foil at 500 ℃ are optimal, and the grain size is moderate after annealing at 500 ℃, which not only ensures sufficient plastic deformation capacity (to promote interfacial mechanical occlusion) during rolling, but also avoids interfacial bonding inhomogeneity caused by oversized grains. Moderate grain density is conducive to the controlled diffusion of elements during the second annealing. Moderate diffusion rate so that the interface to form a thin and continuous layer of intermetallic compounds, both play a reinforcing effect, but did not significantly reduce the plasticity. Partial recrystallization occurs in the second annealing, the formation of fine β-phase grains, to achieve the best match between strength and plasticity. 400 ℃ composite foil mechanical properties are sub-optimal, the original grain size leads to the rolling of high surface activation energy, the interface is tightly coupled, but the grain boundaries are too much to accelerate the diffusion of the elements of the second annealing, the formation of thicker intermetallic compounds layer. Brittle compounds increase to weaken the strength, but the fine grain matrix still provides a certain plasticity. 600 ℃ composite foil mechanical properties of the worst, the original coarse grains reduce the rolling surface plastic deformation capacity, interface mechanical occlusion is not sufficient, the formation of microcracks and other defects. Stress concentration induced interface peeling during secondary annealing. Coarse grains reduce diffusion channels, leading to localized enrichment of elements and the formation of intermetallic compounds. Meanwhile, β-phase coarsening further reduces the strength. As shown in Fig. 4 (4-6), the fracture morphology of the composite foils is characterized by three morphologies according to the C7701 layer, the diffusion layer and the Ti layer. The intermediate Ti layer exhibits obvious along-crystal fracture and a small number of tough nests, which is due to the fact that pure Ti foils with larger grain sizes exhibit tough and brittle fracture behavior during the fracture process. As the grain size increases, it leads to deconvolution cracks sprouting at grain boundaries instead of forming cavities between grains. This leads to rapid expansion of brittle perforation cracks along the direction of deconvolution. These features coexist with a large number of tough nests due to plastic deformation, presenting a tough-brittle coexisting microscopic morphology. The C7701 layer as a whole exhibits the characteristics of ductile fracture, with obvious tough nests and traces of fatigue cracks, which are fatigue toughness fractures induced by irreversible plastic deformation during tensile process. A magnified view of the diffusion interface, as shown in Fig. 4(7-9), shows that the diffusion layer presents flat fracture with less disintegration order, which is due to the multiple intermetallic compounds formed by mutual diffusion of elements in the annealing stage after rolling, which leads to the difficulty of plastic deformation when the material is subjected to external forces, thus forming a very flat fracture along the disintegration surface of the crystal at low energy. At the same time, the disintegration cracks are planar in the crystal, and a single disintegration crack in the grain can simultaneously expand on two parallel disintegration planes, eventually forming a disintegration step. 4. Conclusion 1.The grain size effect has a key regulatory role on the rolling bonding effect and interfacial element diffusion of composite foils. Controlling grain size by changing the pre-roll heat treatment temperature significantly affects the mechanical occlusion and element diffusion behavior at the interface during rolling. Smaller grains provide fast diffusion channels through high-density grain boundaries, which promote interfacial element diffusion gradient and enhance the bonding uniformity, while larger grains cause diffusion obstruction due to the reduction of grain boundaries, which leads to interfacial defects and reduces the bonding strength. 2.The synergistic effect of interfacial elemental diffusion gradients and intermetallic compounds dominates the mechanical properties of composite foils. Moderate elemental diffusion forms a thin and continuous Ti₂Cu/Ti₂Ni intermetallic layer, which improves the interfacial toughness by inhibiting crack propagation while preserving the matrix plasticity. Excessive diffusion leads to thickening of the intermetallic layer and weakening of the strength, while insufficient diffusion exacerbates brittle fracture at the interface due to localized elemental enrichment and coarsening of the β-phase. 3.Grain size effects modulate mechanical properties through a cascade mechanism of rolling compound-diffusion-compound generation. Grain size further affects the secondary annealing diffusion behavior and the distribution and morphology of intermetallic compounds by influencing the rolling deformability. The balance between grain refinement and diffusion rate at 500°C achieves an optimal match of strength-plasticity, while extreme grain sizes (either too fine or too coarse) lead to significant degradation of the mechanical properties due to the concentration of interfacial stresses or insufficient diffusion channels. This mechanism provides a theoretical basis for the gradient grain design of ultra-thin composite foils. Declarations CRediT authorship contribution statement Rui Chen: Writing-original draft, Writing-review & editing. Zhihe Dou: Reviewing, Methodology. Hongmei Zhang: Reviewing, Investigating, Conceptualization. Tingan Zhang: Reviewing, Methodology. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Data availability The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. References M. Geiger, M. Kleiner, R. Eckstein, et al, Microforming. CIRP Annals, 2001, 50(2): 445-462. https://doi.org/10.1016/S0007-8506(07)62991-6. A. S. Hermann, P.C. Zahlen, I. Zuardy. Sandwich structures technology in commercial aviation - present applications and future trends. Sandwich Structures 7: Advancing with Sandwich Structures and Materials, 2005: 13-26. https://doi.org/10.1007/1-4020-3848-8_2. J. R. Vinson. Sandwich Structures. Applied Mechanics Reviews, 2001, 54(3): 201-214. https://doi.org/10.1115/1.3097295. H. R. Lin, Y. Z. Tian, S. J. Sun, et al. Microstructural Evolution and Mechanical Properties of Laminated CuAl Composites Processed by Accumulative Roll-Bonding and Annealing. Acta Metallurgica Sinica (English Letters), 2021, 34: 925-931. https://doi.org/10.1007/s40195 -020-01179-w. T. Q. Mo, J. Chen, Z. J. Chen, et al. Microstructure Evolution During Roll Bonding and Growth of Interfacial Intermetallic Compounds in Al/Ti/Al Laminated Metal Composites. JOM, 2019, 71: 4769-4777. https://doi.org/10.1007/s11837-019-03845-6. Z. C. Luo, Q. Zhang, X. Y. Ma, et al. Microstructure evolution process of Ferro-Aluminum based sandwich composite for electromagnetic shielding.Micron, 2014, 64: 34-38. https://doi.org/10.1016/j.micron.2014.04.003. H. M. Yang, P. X. Zhu, S. G. Zhou, et al. Preliminary Research on Interfacial Evolution Behaviour of Ti-Cu Laminated Composite Materials. Advanced Materials Research, 2011,194-196: 1615-1619. https://doi.org/10.4028/www.scientific.net/AMR.194-196.1615. H. Inoue, M. Ishio, T. Takasugi. Texture of TiNi shape memory alloy sheets produced by roll-bonding and solid phase reaction from elementary metals. Acta Materialia, 2003, 51(20): 6373-6383. https://doi.org/10.1016/j.actamat.2003.08.009. S. Jiang, R. L. Peng, N. Jia, et al. Microstructural and textural evolutions in multilayered Ti/Cu composites processed by accumulative roll bonding. Journal of Materials Science & Technology, 2019, 35(6): 1165-1174. https://doi.org/10.1016/j.jmst.2018.12.018. B. Zhang, L. Wang , X. H. Zhang, et al. Microstructure Evolution and Mechanical Properties of the Ti/Ni Multilayer Composite Produced by Accumulative Roll Bonding. Rare Metal Materials and Engineering, 2016, 45(9): 2352-2358. R. Imayev, N. Gabdullin, G. Salishchev. Effect of grain size on superplasticity of an intermetallic Ti 3 Al compound. Intermetallics, 1997, 5(3): 229-236. https://doi.org/10.1016/S09 66-9795(96)00085-4. V. Lacaille, C. Morel, E. Feulvarch, et al. Finite element analysis of the grain size effect on diffusion in polycrystalline materials. Computational Materials Science, 2014, 95: 187-191. https://doi.org/10.1016/j.commatsci.2014.07.026. Y. G. Liu , J. Q. Zhou, Effect of Grain Size Distribution on the Local Mechanical Behavior of Nanocrystalline Materials. Materials Science Forum, 2011, 682: 153-158. https://doi.org/ 10.4028/www.scientific.net/MSF.682.153. H. W. Liu, J. P. Lu, M. R. Zheng, et al, Size effects on metal-insulator phase transition in individual vanadium dioxide nanowires. Optics Express, 2014, 22(25): 30748-30755. https://doi.org/10.1364/OE.22.030748. D. Palai, A. Dey, P. Bera, et al. Comprehensive studies on microstructural, electronic, thermo-optical, mechanical and tribological behavious of vacuum heat treated ultra thin CP Ti foils. Materials Research Express, 2017, 4(7): 076404. https://doi.org/10.1088/2053-1591/aa75b1. F. J. Gil, C. Aparicio, J. A. Planell. Effect of oxygen content on grain growth kinetics of titanium. Journal of Materials Synthesis and Processing, 2002, 10(5): 263-266. https://doi.org/10.1023/A:1023094126132. P. Pripanapong, L. Tachai. Microstructure and Mechanical Properties of Sintered Ti-Cu Alloys. Advanced Materials Research, 2010, 93-94: 99-104. https://doi.org/10.4028/www. scientific.net/AMR.93-94.99. S. Chatterjee, T.A. Abinandanan, K. Chattopadhyay. Phase formation in Ti/Ni dissimilar welds. Materials Science and Engineering: A, 2008, 490(1-2): 7-15. https://doi.org/10.1016/j. msea.2007.12.041. Z. X. Deng, K. Xu, Y. Y. Tian, et al. Experimental investigation and thermodynamic re-assessment of the Ti–Zn system and atomic mobility of its bcc phase. Calphad, 2022, 76: 102392. https://doi.org/10.1016/j.calphad.2022.102392. 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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-6273194","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":433183997,"identity":"611b79db-a639-4f9d-9d61-cdc22df4706c","order_by":0,"name":"Rui Chen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Chen","suffix":""},{"id":433183998,"identity":"8a4942a8-5a21-4918-8a26-74f1a90c85a0","order_by":1,"name":"Zhihe Dou","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Zhihe","middleName":"","lastName":"Dou","suffix":""},{"id":433183999,"identity":"2dffd793-5458-4a08-b318-7cf904fe7c97","order_by":2,"name":"Honemei Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA20lEQVRIiWNgGAWjYDACCSBmbGCQA1EHGBiYiddiDFJNmpbEBqK1yM9ufvbw645t6RvOnz9wgKHCOrGB/ewBvFoY5xwzN5Y9czt3w41koC1n0hMbePIS8Gphlkgwk5ZsA2kBOoyx7XBigwSPAV4tbBLp30Ba0g3OHwZq+UeEFh6JHDPJj223EwwOAB3G2ECEFgmJnDJpxrbbhjNvJBscSDiWbtzGk4Nfi/yM9G2SP9tuy/OdP/jwwYcaa9l+9jP4tYAAMw+MlQDyHUH1QMD4gxhVo2AUjIJRMHIBAKyLSS7ioq7FAAAAAElFTkSuQmCC","orcid":"","institution":"university of science and technology liaoning","correspondingAuthor":true,"prefix":"","firstName":"Honemei","middleName":"","lastName":"Zhang","suffix":""},{"id":433184000,"identity":"ac517139-42ff-4016-b869-2e0abcc49ec2","order_by":3,"name":"Tingan Zhang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Tingan","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2025-03-21 02:03:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6273194/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6273194/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79768315,"identity":"f45f9f2c-75b7-4d93-a112-95fff1e061f9","added_by":"auto","created_at":"2025-04-02 12:49:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":196626,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental Flowchart\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6273194/v1/145ac4f0ed30a76787668ac9.png"},{"id":79768317,"identity":"d68a850a-8aea-4b0c-8773-328217ec6dd6","added_by":"auto","created_at":"2025-04-02 12:49:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2749492,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of the foils.\u003c/p\u003e\n\u003cp\u003e(1)-(3) C7701 foil annealed at different temperatures. (1) 400°C (2) 500°C (3) 600°C;\u003c/p\u003e\n\u003cp\u003e(4)-(6) Pure titanium foil annealed at different temperatures. (4) 400°C (5) 500°C (6) 600°C;\u003c/p\u003e\n\u003cp\u003e(7)-(9) Composite foil in polished state. (7) 400°C (8) 500°C (9) 600°C;\u003c/p\u003e\n\u003cp\u003e(10)-(12) Composite foil in the corroded state. (10) 400°C (11) 500°C (12) 600°C;\u003c/p\u003e\n\u003cp\u003e(13)-(15) SEM image of composite foil interface. (13) 400°C (14) 500°C (15) 600°C;\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6273194/v1/77f834f3a5411e8d3833eeb8.png"},{"id":79769162,"identity":"60a6e797-433c-4e8d-ac8a-85942aa206d3","added_by":"auto","created_at":"2025-04-02 12:57:34","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":944410,"visible":true,"origin":"","legend":"\u003cp\u003eElemental distribution and XRD spectra of composite foils\u003c/p\u003e\n\u003cp\u003e(1)-(3) Point scan and line scan positions of elements. (1) 400°C (2) 500°C (3) 600°C\u003c/p\u003e\n\u003cp\u003e(4)-(6) Curves of elemental line scanning results. (4) 400°C (5) 500°C (6) 600°C\u003c/p\u003e\n\u003cp\u003e(7)-(9) Spectra of elemental point scanning results. (7) 400°C (8) 500°C (9) 600°C\u003c/p\u003e\n\u003cp\u003e(10)-(12) Distribution of elemental surface scans. (10) 400°C (11) 500°C (12) 600°C\u003c/p\u003e\n\u003cp\u003e(13) XRD spectra of composite foils.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6273194/v1/7f1482fe94c162e09174b73c.png"},{"id":79768318,"identity":"3d3b5808-82d1-4056-aa97-fa168628c931","added_by":"auto","created_at":"2025-04-02 12:49:34","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":782028,"visible":true,"origin":"","legend":"\u003cp\u003eMechanical property curves and fracture morphology of composite foils\u003c/p\u003e\n\u003cp\u003e(1)-(3) Mechanical property curves of composite foils. (1) 400°C (2) 500°C (3) 600°C\u003c/p\u003e\n\u003cp\u003e(4)-(6) Overall fracture morphology of composite foils. (4) 400°C (5) 500°C (6) 600°C\u003c/p\u003e\n\u003cp\u003e(7)-(9) Fracture morphology at the interface of composite foils. (7) 400°C (8) 500°C (9) 600°C\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6273194/v1/2406b99b77087cb69bbffc4b.png"},{"id":86854768,"identity":"afed4abb-5990-4a1a-b120-353ccfb2220d","added_by":"auto","created_at":"2025-07-16 10:41:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5173895,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6273194/v1/a3efa414-0879-40d5-9f24-76293392328c.pdf"}],"financialInterests":"","formattedTitle":"Grain size effect on the mechanical properties of C7701/Ti/C7701 ultra-thin composite foils by influencing element diffusion","fulltext":[{"header":"1.Introduction","content":"\u003cp\u003eMicroforming technology is a technique suitable for the production of extremely small metal parts with clear economic and ecological advantages in many industrial product applications. The fundamental challenge in microforming systems stems from the pronounced size effect phenomenon, which manifests dual influences on both localized deformation mechanisms and global process stability. Addressing this technological barrier necessitates an integrated multidisciplinary framework that synthesizes advancements from electronic control systems, precision mechanical engineering, physical modeling techniques, surface chemistry interactions, and advanced material characterization methodologies [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSandwich structures are more efficient than conventional designs of longitudinal stiffeners and stabilizing ring structures using a double-layer structure with an intermediate stabilizing medium. Sandwich structures are favored because of their higher flexural stiffness to weight ratio, lower transverse deformation, and higher yield resistance [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe production of sandwich materials mainly utilizes rolled composite technology, and the bonding interface will inevitably generate diffusion layers and a variety of intermetallic compounds during the production process, which have an important impact on the performance of sandwich materials.[\u003cspan additionalcitationids=\"CR5 CR6 CR7\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eMeanwhile, the multilayer rolling composite technology can further promote the grain refinement of the sandwich material. Jiang et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] successfully prepared bulk Ti/Cu composites by ARB process and found that multilayer composite rolling can achieve grain refinement. Zhang et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] prepared Ti/Ni multilayer composite plate materials by ARB method using industrial pure Ti and pure Ni plates as initial materials. With the increase of rolling passes, the microstructure refinement of Ti and Ni layers in the composites was obvious and the degree of uniformity was improved.\u003c/p\u003e \u003cp\u003eThe grain refinement and intermetallic compounds generated in the interlayer have a significant effect on the mechanical properties of composite plates. Imayev et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] found that the effect of intermetallic compounds on the mechanical properties of the material is affected by the size of the grain size, and the reduction of grain size and increase in grain boundary area resulted in the Ti3Al intermetallic compounds reducing the formation of voids during the flow process. Lacaille et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] found that the refinement of the grain size enhances the diffusional properties of the material because of the increase in the density of the grain boundaries, which in turn increases the macroscopic diffusivity. The grain boundaries are fast diffusion channels in the material. Liu et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] found that the local strain in small-sized materials is dependent on the grain size and is heterogeneous across different grain sizes. As the macroscopic strain increases, the effect of grain size on the local strain increases and the difference in local strain between different grains becomes more pronounced.\u003c/p\u003e \u003cp\u003eMost of the studies on sandwich structures focus on the preparation methods and performance characterization of conventional sizes, while there are fewer studies on the effects of grain size effects on the rolled composite behavior and performance of sandwich structures under ultra-thin composite foils. In this study, the micro-rolled composite behavior of two metal foils, the generation of intermetallic compounds in the bond layer of composite foils were analyzed in combination with the micro-rolled composite technology, and the mechanical properties of composite foils under the influence of a variety of complex factors were investigated. The influence of grain size effect on the mechanical properties of composite foils by affecting the microstructure of the composite foil bonding layer is investigated.\u003c/p\u003e"},{"header":"2.Equipment and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Equipment\u003c/h2\u003e \u003cp\u003eThe GR-TF60/18 heat treatment furnace from China was selected for the heat treatment of titanium foil. For tensile testing, the XK-207s microtensile machine from China was used. The KEYENCE VHX-5000 Super Depth of Field Microscope from Japan was used for metallographic analysis. The S7-300 four-roll mill from China was used for rolling compound. Zeiss Sigma 300 scanning electron microscope from Germany was selected for SEM inspection.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental methods\u003c/h2\u003e \u003cp\u003eThe raw material for the heat treatment is pure titanium foil and C7701 foil with a thickness of 0.05 mm, a length of 80 mm and a width of 10 mm. Annealing was carried out in argon gas at temperatures of 400, 500 and 600\u0026deg;C, respectively, with a holding time of 1h, to obtain foils with different grain sizes and microstructures. The annealing process is carried out in a sealed environment, after the end of the insulation, pass into the room temperature argon gas flow as a cooling medium, to isolate the oxygen penetration at the same time to ensure the cooling efficiency. Titanium foils and C7701 foils annealed at different temperatures were subjected to metallographic observation to analyze the difference in microstructure at different temperatures, and the grain size of pure titanium foils annealed at different temperatures. Titanium foils and C7701 foils with the same annealing temperature were used as a group as the raw material for rolling, and were divided into 3 groups. Each group was stacked and combined in an arrangement of C7701/Ti/C7701 and rolled for lamination at a rolling force of 800N. After rolling, the composite foils were uniformly annealed at 600\u0026deg;C for the second annealing to ensure good diffusion of the interface layer. XRD analysis of the composite foil was carried out in the detection range of 20\u0026deg;-100\u0026deg; for 2 min to further determine the internal structure and organizational transformation of composite foil. Metallographic and SEM tests were carried out on the annealed composite foils to determine the rolling bond quality and elemental distribution. Microtensile tests were carried out on the composite foils at a crosshead speed of 0.1 mm/min to analyze the mechanical properties of the foils and the effects of grain size before rolling and microstructure after rolling on the mechanical properties. The experimental flow is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3.Results and discussion","content":"\u003cp\u003eAs can be seen from Fig. 2 (1-6), the microstructure of C7701 foil annealed at 400\u0026deg;C retains grains distributed along the rolling direction, and the theoretical recrystallization temperature of C7701 is 483\u0026deg;C. It is obvious that C7701 foil fails to recrystallize at 400\u0026deg;C, and single equiaxed grains are generated in C7701 foil annealed at 500\u0026deg;C and 600\u0026deg;C, and the grain size increases with the increase of the annealing temperature. The grain sizes were calculated to be 7.1 \u0026mu;m (500\u0026deg;C) and 17.3 \u0026mu;m (600\u0026deg;C), respectively.\u003c/p\u003e\n\u003cp\u003eThe grain size of pure titanium increases with increasing annealing temperature. The grain sizes were 6.4 \u0026mu;m (400 ℃), 7.5 \u0026mu;m (500 ℃) and 16.7 \u0026mu;m (600 ℃), respectively. The titanium foil annealed at 600 ℃ produced needle-like \u0026beta;-phases at the grain boundaries. The theoretical phase transition temperature of pure titanium is 882 ℃, but the material size, cooling rate, annealing atmosphere and other factors affect the actual phase transition temperature of pure titanium. The smaller material size represents a smaller number of grains, a larger surface area, an increase in the proportion of surface atoms, and a higher surface energy, which reduces the phase transformation temperature [14,15]. Due to the grain size effect, the reduction in the number of grains leads to a consequent reduction in the number of grain boundaries, which reduces the hindrance to dislocation motion and the energy required for phase transformation, thus further reducing the phase transformation temperature. During the annealing process, argon was used as a protective atmosphere for annealing in a confined space, and a room temperature argon gas stream was introduced for cooling at the end of the holding period, which ensured the cooling efficiency and insulated the infiltration of oxygen. The possibility of oxygen dissolution into the pure titanium lattice was further prevented and lattice distortion was reduced, resulting in the generation of the \u0026beta;-phase at lower temperatures [16]. At the same time, due to the extremely low thickness of the material, the heat dissipation efficiency is further improved and the cooling rate is accelerated, which is conducive to the retention of the \u0026beta;-phase organization. Under the combined influence of these factors, the generation of the \u0026beta;-phase at a lower temperature than the theoretical phase transition temperature was finally realized.\u003c/p\u003e\n\u003cp\u003eFrom Fig. 2 (7-12), it can be seen that the composite foil in the polished state has no obvious cracking, and there exists a clear demarcation line between C7701 and Ti. For the composite foil at 600 ℃ before rolling, the jagged structure at the interface is more obvious, which is due to the larger grain size at 600 ℃, and the intensification of the grain ruler effect leads to uneven deformation, which produces a jagged bonding interface. After corrosion of the sample bonding interface color is darker, this is due to the process of heat treatment of the two materials elements diffuse each other to form a variety of elements mixed bonding layer, and at the same time by the two corrosive agents and darker color.\u003c/p\u003e\n\u003cp\u003eFig 2 (13-15) shows the backscattering pictures of the composite foil, which can clearly show that there is an obvious elemental lining at the interface, which further confirms that the elements of the two materials diffuse into each other during heat treatment, and at the same time, it can be seen that at higher multiplicity, the samples at 600\u0026deg;C before rolling are affected by the grain size effect, and there is an obvious rupture at the interface.\u003c/p\u003e\n\u003cp\u003eAccording to the position of the asterisk in Fig. 3 (1-3), elemental point scanning is carried out at the interface of the composite foil, elemental line scanning is carried out perpendicular to the direction of the interface according to the position of the yellow line, and surface scanning is carried out to analyze the composite foil. Fig. 3 (4-6) shows that the elemental diffusion of the composite foil is not a cliff-like decline, proving that there is a certain gradient of elemental diffusion. The line scan results show that the Cu and Ni elements show a tendency of rising and then falling at the interface, and the surface scan results in Fig. 3 (10-12) show that the Cu and Ni elements have obvious aggregation phenomenon in the interfacial layer, whereas the point scan results in Fig. 3 (7-9) show that the Zn element exists less at the interface, which is almost negligible, and is mainly dominated by the Ti, Cu and Ni elements.\u003c/p\u003e\n\u003cp\u003eCompared with the single-layer foil, the grain size of the composite foil is significantly reduced and an element diffusion layer is formed at the interface. Affected by the physical form of the sandwich structure, the growth of grains is limited by the space, so that the grain size of the composite foil is smaller, and at the same time by the grain size effect, the interface part of the rolling process due to uneven distribution of grains will produce a random distribution of stress concentration, and in the annealing process after rolling by the influence of the interface effect, the interface of the stress concentration at the interface will promote the nucleation of the new grains, further limiting the growth of the grains. The high temperature environment during the annealing process provides sufficient energy for metal atoms to migrate near the interface. This migration allows atoms originally present in each material to cross the interface into the other material, where elemental diffusion occurs.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 3 (13), XRD examination of the samples, combined with the Ti-Cu, Ti-Ni, Ti-Zn binary phase diagrams [17-19] and EDS point-scan mass ratios, as well as the heat treatment process, it can be determined that intermetallic compounds dominated by Ti2Cu and Ti2Ni have been generated at the interface.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDifferent intermetallic compounds have different effects on the material properties, in this paper, the diffusion and binding of elements basically occurs in the elemental diffusion layer between the two foil layers, which indicates that the distribution of intermetallic compounds is strictly limited to the diffusion layer part. The mixing of intermetallic compounds with different properties in a smaller space further cuts the elemental distribution of the composite foil.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 4 (1-3), the mechanical properties of the composite foil at 500 ℃ are optimal, and the grain size is moderate after annealing at 500 ℃, which not only ensures sufficient plastic deformation capacity (to promote interfacial mechanical occlusion) during rolling, but also avoids interfacial bonding inhomogeneity caused by oversized grains. Moderate grain density is conducive to the controlled diffusion of elements during the second annealing. Moderate diffusion rate so that the interface to form a thin and continuous layer of intermetallic compounds, both play a reinforcing effect, but did not significantly reduce the plasticity. Partial recrystallization occurs in the second annealing, the formation of fine \u0026beta;-phase grains, to achieve the best match between strength and plasticity. 400 ℃ composite foil mechanical properties are sub-optimal, the original grain size leads to the rolling of high surface activation energy, the interface is tightly coupled, but the grain boundaries are too much to accelerate the diffusion of the elements of the second annealing, the formation of thicker intermetallic compounds layer. Brittle compounds increase to weaken the strength, but the fine grain matrix still provides a certain plasticity. 600 ℃ composite foil mechanical properties of the worst, the original coarse grains reduce the rolling surface plastic deformation capacity, interface mechanical occlusion is not sufficient, the formation of microcracks and other defects. Stress concentration induced interface peeling during secondary annealing. Coarse grains reduce diffusion channels, leading to localized enrichment of elements and the formation of intermetallic compounds. Meanwhile, \u0026beta;-phase coarsening further reduces the strength.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 4 (4-6), the fracture morphology of the composite foils is characterized by three morphologies according to the C7701 layer, the diffusion layer and the Ti layer. The intermediate Ti layer exhibits obvious along-crystal fracture and a small number of tough nests, which is due to the fact that pure Ti foils with larger grain sizes exhibit tough and brittle fracture behavior during the fracture process. As the grain size increases, it leads to deconvolution cracks sprouting at grain boundaries instead of forming cavities between grains. This leads to rapid expansion of brittle perforation cracks along the direction of deconvolution. These features coexist with a large number of tough nests due to plastic deformation, presenting a tough-brittle coexisting microscopic morphology. The C7701 layer as a whole exhibits the characteristics of ductile fracture, with obvious tough nests and traces of fatigue cracks, which are fatigue toughness fractures induced by irreversible plastic deformation during tensile process.\u003c/p\u003e\n\u003cp\u003eA magnified view of the diffusion interface, as shown in Fig. 4(7-9), shows that the diffusion layer presents flat fracture with less disintegration order, which is due to the multiple intermetallic compounds formed by mutual diffusion of elements in the annealing stage after rolling, which leads to the difficulty of plastic deformation when the material is subjected to external forces, thus forming a very flat fracture along the disintegration surface of the crystal at low energy. At the same time, the disintegration cracks are planar in the crystal, and a single disintegration crack in the grain can simultaneously expand on two parallel disintegration planes, eventually forming a disintegration step.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003e1.The grain size effect has a key regulatory role on the rolling bonding effect and interfacial element diffusion of composite foils. Controlling grain size by changing the pre-roll heat treatment temperature significantly affects the mechanical occlusion and element diffusion behavior at the interface during rolling. Smaller grains provide fast diffusion channels through high-density grain boundaries, which promote interfacial element diffusion gradient and enhance the bonding uniformity, while larger grains cause diffusion obstruction due to the reduction of grain boundaries, which leads to interfacial defects and reduces the bonding strength.\u003c/p\u003e\n\u003cp\u003e2.The synergistic effect of interfacial elemental diffusion gradients and intermetallic compounds dominates the mechanical properties of composite foils. Moderate elemental diffusion forms a thin and continuous Ti₂Cu/Ti₂Ni intermetallic layer, which improves the interfacial toughness by inhibiting crack propagation while preserving the matrix plasticity. Excessive diffusion leads to thickening of the intermetallic layer and weakening of the strength, while insufficient diffusion exacerbates brittle fracture at the interface due to localized elemental enrichment and coarsening of the \u0026beta;-phase.\u003c/p\u003e\n\u003cp\u003e3.Grain size effects modulate mechanical properties through a cascade mechanism of rolling compound-diffusion-compound generation. Grain size further affects the secondary annealing diffusion behavior and the distribution and morphology of intermetallic compounds by influencing the rolling deformability. The balance between grain refinement and diffusion rate at 500\u0026deg;C achieves an optimal match of strength-plasticity, while extreme grain sizes (either too fine or too coarse) lead to significant degradation of the mechanical properties due to the concentration of interfacial stresses or insufficient diffusion channels. This mechanism provides a theoretical basis for the gradient grain design of ultra-thin composite foils.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRui Chen:\u003c/strong\u003e Writing-original draft, Writing-review \u0026amp; editing. \u003cstrong\u003eZhihe Dou:\u003c/strong\u003e Reviewing, Methodology. \u003cstrong\u003eHongmei Zhang:\u003c/strong\u003e Reviewing, Investigating, Conceptualization. \u003cstrong\u003eTingan Zhang:\u003c/strong\u003e Reviewing, Methodology.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eM. Geiger, M. Kleiner, R. Eckstein, et al, Microforming. CIRP Annals, 2001, 50(2): 445-462. https://doi.org/10.1016/S0007-8506(07)62991-6.\u003c/li\u003e\n \u003cli\u003eA. S. Hermann, P.C. Zahlen, I. Zuardy. Sandwich structures technology in commercial aviation - present applications and future trends. Sandwich Structures 7: Advancing with Sandwich Structures and Materials, 2005: 13-26. https://doi.org/10.1007/1-4020-3848-8_2.\u003c/li\u003e\n \u003cli\u003eJ. R. Vinson. Sandwich Structures. Applied Mechanics Reviews, 2001, 54(3): 201-214. https://doi.org/10.1115/1.3097295.\u003c/li\u003e\n \u003cli\u003eH. R. Lin, Y. Z. Tian, S. J. Sun, et al. Microstructural Evolution and Mechanical Properties of Laminated CuAl Composites Processed by Accumulative Roll-Bonding and Annealing. Acta Metallurgica Sinica (English Letters), 2021, 34: 925-931. https://doi.org/10.1007/s40195 -020-01179-w.\u003c/li\u003e\n \u003cli\u003eT. Q. Mo, J. Chen, Z. J. Chen, et al. Microstructure Evolution During Roll Bonding and Growth of Interfacial Intermetallic Compounds in Al/Ti/Al Laminated Metal Composites. JOM, 2019, 71: 4769-4777. https://doi.org/10.1007/s11837-019-03845-6.\u003c/li\u003e\n \u003cli\u003eZ. C. Luo, Q. Zhang, X. Y. Ma, et al. Microstructure evolution process of Ferro-Aluminum based sandwich composite for electromagnetic shielding.Micron, 2014, 64: 34-38. https://doi.org/10.1016/j.micron.2014.04.003.\u003c/li\u003e\n \u003cli\u003eH. M. Yang, P. X. Zhu, S. G. Zhou, et al. Preliminary Research on Interfacial Evolution Behaviour of Ti-Cu Laminated Composite Materials. Advanced Materials Research, 2011,194-196: 1615-1619. https://doi.org/10.4028/www.scientific.net/AMR.194-196.1615.\u003c/li\u003e\n \u003cli\u003eH. Inoue, M. Ishio, T. Takasugi. Texture of TiNi shape memory alloy sheets produced by roll-bonding and solid phase reaction from elementary metals. Acta Materialia, 2003, 51(20): 6373-6383. https://doi.org/10.1016/j.actamat.2003.08.009.\u003c/li\u003e\n \u003cli\u003eS. Jiang, R. L. Peng, N. Jia, et al. Microstructural and textural evolutions in multilayered Ti/Cu composites processed by accumulative roll bonding. Journal of Materials Science \u0026amp; Technology, 2019, 35(6): 1165-1174. https://doi.org/10.1016/j.jmst.2018.12.018.\u003c/li\u003e\n \u003cli\u003eB. Zhang, L. Wang , X. H. Zhang, et al. Microstructure Evolution and Mechanical Properties of the Ti/Ni Multilayer Composite Produced by Accumulative Roll Bonding. Rare Metal Materials and Engineering, 2016, 45(9): 2352-2358.\u003c/li\u003e\n \u003cli\u003eR. Imayev, N. Gabdullin, G. Salishchev. Effect of grain size on superplasticity of an intermetallic Ti\u003csub\u003e3\u003c/sub\u003eAl compound. Intermetallics, 1997, 5(3): 229-236. https://doi.org/10.1016/S09 66-9795(96)00085-4.\u003c/li\u003e\n \u003cli\u003eV. Lacaille, C. Morel, E. Feulvarch, et al. Finite element analysis of the grain size effect on diffusion in polycrystalline materials. Computational Materials Science, 2014, 95: 187-191. https://doi.org/10.1016/j.commatsci.2014.07.026.\u003c/li\u003e\n \u003cli\u003eY. G. Liu , J. Q. Zhou, Effect of Grain Size Distribution on the Local Mechanical Behavior of Nanocrystalline Materials. Materials Science Forum, 2011, 682: 153-158. https://doi.org/ 10.4028/www.scientific.net/MSF.682.153.\u003c/li\u003e\n \u003cli\u003eH. W. Liu, J. P. Lu, M. R. Zheng, et al, Size effects on metal-insulator phase transition in individual vanadium dioxide nanowires. Optics Express, 2014, 22(25): 30748-30755. https://doi.org/10.1364/OE.22.030748.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eD. Palai, A. Dey, P. Bera, et al. Comprehensive studies on microstructural, electronic, thermo-optical, mechanical and tribological behavious of vacuum heat treated ultra thin CP Ti foils. Materials Research Express, 2017, 4(7): 076404. https://doi.org/10.1088/2053-1591/aa75b1.\u003c/li\u003e\n \u003cli\u003eF. J. Gil, C. Aparicio, J. A. Planell. Effect of oxygen content on grain growth kinetics of titanium. Journal of Materials Synthesis and Processing, 2002, 10(5): 263-266. https://doi.org/10.1023/A:1023094126132.\u003c/li\u003e\n \u003cli\u003eP. Pripanapong, L. Tachai. Microstructure and Mechanical Properties of Sintered Ti-Cu Alloys. Advanced Materials Research, 2010, 93-94: 99-104. https://doi.org/10.4028/www. scientific.net/AMR.93-94.99.\u003c/li\u003e\n \u003cli\u003eS. Chatterjee, T.A. Abinandanan, K. Chattopadhyay. Phase formation in Ti/Ni dissimilar welds. Materials Science and Engineering: A, 2008, 490(1-2): 7-15. https://doi.org/10.1016/j. msea.2007.12.041.\u003c/li\u003e\n \u003cli\u003eZ. X. Deng, K. Xu, Y. Y. Tian, et al. Experimental investigation and thermodynamic re-assessment of the Ti\u0026ndash;Zn system and atomic mobility of its bcc phase. Calphad, 2022, 76: 102392. https://doi.org/10.1016/j.calphad.2022.102392.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Micro forming, composite foil, Size effect, Sandwich structure, Mechanical property","lastPublishedDoi":"10.21203/rs.3.rs-6273194/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6273194/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWith the increasing application of titanium and copper alloy materials and various sandwich composites in various precision machining fields, it has become increasingly important to study the complex changes in the internal microstructure of sandwich composites and their influencing factors during the microforming process. In this study, titanium and C7701 foils were heat-treated at different temperatures to obtain raw materials with different grain sizes and microstructures. The heat-treated foils were rolled into a sandwich structure in a C7701 / Ti / C7701 arrangement and the composite foil was annealed at the same temperature. Metallographic and SEM tests on the composite foils showed that the titanium and C7701 rolled laminates were well bonded at 400℃ and 500℃ before rolling, and there was a certain gradient of elemental diffusion in the bonded layer, and the XRD test showed that a variety of intermetallic compounds were produced in the bonded layer. By analyzing the element diffusion and intermetallic compound generation at the interface of composite foils and conducting microtensile mechanical property tests on composite foils, it is found that the grain size before rolling the composite has an important influence on the interfacial bonding and element diffusion of composite foils, which in turn affects the mechanical properties of composite foils.\u003c/p\u003e","manuscriptTitle":"Grain size effect on the mechanical properties of C7701/Ti/C7701 ultra-thin composite foils by influencing element diffusion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-02 12:49:29","doi":"10.21203/rs.3.rs-6273194/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3312ca48-95f6-4d08-b340-4ba3dbb0928d","owner":[],"postedDate":"April 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-16T10:33:45+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-02 12:49:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6273194","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6273194","identity":"rs-6273194","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}