Recently, the team led by Prof. Chen Jun from the Institute of Forming Technology and Equipment, School of Materials Science and Engineering, Shanghai Jiao Tong University, has developed a novel hybrid process that synchronously integrates incremental sheet forming and friction stir additive manufacturing (AM-ISF), and successfully fabricated high-performance Steel/Al heterogeneous thin-walled components. By ingeniously harnessing the synergistic strengthening effects of hetero-deformation induced (HDI) stress and back stress activated by the multi-scale bioinspired heterogeneous structures in situ generated within the material, this work systematically addresses the core challenges inherent in conventional manufacturing of dissimilar metals—such as lengthy prototyping cycles, high tooling costs, and cracking caused by severe deformation incompatibility. It provides a brand-new paradigm for the integrated manufacturing, comprehensive performance enhancement, and engineering application of high-performance heterogeneous thin-walled components. The related research, entitled "A novel incremental forming method coupled with additive manufacturing for heterogeneous Steel/Al laminated structures," has been published in the International Journal of Machine Tools and Manufacture (IF 18.8), a top-tier journal in the field of manufacturing science and technology. The first author of the paper is Dr. Chang Zhidong (Assistant Researcher), and the corresponding authors are Assoc. Prof. Geng Peihao (School of Mechanical Engineering) and Prof. Chen Jun (School of Materials Science and Engineering). Paper link: https://doi.org/10.1016/j.ijmachtools.2026.104409.
Heterogeneous metal thin-walled components (e.g., Steel/Al dissimilar laminated sheets) effectively integrate the performance advantages of different constituent metals, offering broad application prospects in structural lightweighting and functional integration in aerospace, modern transportation, and other fields. However, the conventional "bonding first, then forming" sequential manufacturing route suffered from excessively long overall development cycles, high tooling costs, and severe deformation incompatibility between constituents, which readily induce local defects such as interfacial delamination, cracking, or wrinkling during subsequent forming. Existing flexible, die-less manufacturing approaches (e.g., conventional incremental forming or standalone additive manufacturing technologies) often struggled to simultaneously guarantee macroscopic forming quality and microscopic interlaminar bonding strength. Consequently, breaking through the process barrier between "forming" and "layer-by-layer bonding" to achieve efficient, flexible, and integrated manufacturing of high-performance heterogeneous metal components has long been a challenging puzzle in this field.
To address the above challenge, the research team innovatively proposed a novel die-less, digitally-driven hybrid manufacturing technique (AM-ISF) that synchronously integrates "forming–joining–additive manufacturing," with the basic principle illustrated in Figure 1. During the process, a rotating tool head incrementally formed the base steel sheet; simultaneously, the intense frictional stirring heat and normal pressure derived the underlying aluminum alloy powder to undergo progressive densification and solid-state recrystallization at temperatures below its melting point. The aluminum layer was thereby densified layer by layer and concurrently achieves in situ metallurgical bonding with the steel substrate, ultimately realizing the one-step integrated manufacturing of high-performance bioinspired heterogeneous components.
Figure 1 Schematic of the "Forming–Joining–Additive Manufacturing" synchronous hybrid process (AM-ISF).
Inspired by the exceptional load-bearing and impact-resistant biological structure of "bone–cartilage" in human joints, the team successfully constructed multi-scale bioinspired heterogeneous structures in situ within the component material by tailoring the macro-micro thermo-mechanical coupled field: a dual-gradient grain structure in the steel matrix, a bimodal grain structure in the aluminum matrix, and a wavy interfacial texture at the heterogeneous bonding interface, as shown in Figures 2 and 3. Through this multi-scale bioinspired heterogeneous structural design, the overall mechanical properties of the matrix materials and the load-transfer stability across the bonding interface were both enhanced, thereby fully realizing the synergistic strengthening-toughening effect of the heterogeneous metal component.
Figure 2 "Bone–Cartilage" bioinspired multi-scale heterogeneous structure.
Figure 3 Interfacial micro-morphology of the multi-scale bioinspired heterogeneous structure.
Experimental tests demonstrated that the heterogeneous material fabricated by AM-ISF exhibits outstanding comprehensive mechanical properties: the tensile yield strength and ultimate tensile strength reached 437 MPa and 580 MPa, respectively, and the interfacial shear strength was as high as 112 MPa, significantly outperforming heterogeneous materials produced by conventional manufacturing methods, as shown in Figure 4. This is attributed to the fact that within the multi-scale heterogeneous material, substantial accumulation of geometrically necessary dislocations (GNDs) is induced by the grain size non-uniformity and microstructural mismatch between hard and soft domains. Notably, the back stress contribution to the hetero-deformation induced (HDI) stress accounted for as much as 76%. This multi-scale back-stress strengthening mechanism remarkably enhances the synergistic strength–ductility capability of the heterogeneous material at the microscopic level.
Figure 4 Mechanical performance of the multi-scale heterogeneous material.
Using this novel approach, the research team has successfully fabricated a variety of complex heterogeneous thin-walled components, including Steel/Al and Ti/Al systems, and no interlaminar delamination or macroscopic cracking failure was observed in regions featuring curved surface transitions or severe deformation, further validating the process's applicability to complex industrial components, as shown in Figure 5. Future work will focus on extending this process to more complex material systems such as fiber/metal multi-phase composites, and on developing a high-fidelity, full-process integrated "process–microstructure–property" predictive model under cyclic thermo-mechanical coupled fields.
Figure 5 Demonstration of integrated flexible manufacturing of complex thin-walled components.