Deformation temperature-driven evolution of microstructure, interface, mechanical, and electrical properties in Al/Cu hybrid conductors: Revealing interfacial extruded Cu regions

Multilayer metallic composites have attracted considerable interest within scientific and industrial communities owing to their superior synergistic properties and suitability for advanced engineering applications. In this study, Al/Cu multilayer hybrid composites are fabricated via roll bonding at three deformation temperatures (25, 250, and 350 °C) to investigate their effects on microstructural evolution, interfacial characteristics, and resultant mechanical and electrical properties. The results indicate that at a deformation temperature of 350 °C, a unique bonding mechanism emerges, characterized by the formation of interfacial extruded Cu regions containing nanoscale grains (<100 nm) at the Al/Cu interface. This phenomenon represents a novel interfacial evolution pathway in roll-bonded Al/Cu composites. Deformation bands in the Al layers significantly promote dynamic recrystallization (DRX) by initiating subgrain formation and facilitating the misorientation necessary for grain boundary transformation. By contrast, DRX is absent in Cu layers owing to limited recovery/ boundary mobility. The maximum improvements in the yield and ultimate tensile strengths are achieved at room temperature (25 °C), with enhancements of 187 % (140 MPa) and 93 % (184 MPa), respectively, relative to rule-of-mixtures predictions. The sample processed at 350 °C exhibits the highest electrical conductivity of 73.4 % International Annealed Copper Standard, which is a 15.6 % enhancement relative to the baseline Al. Work hardening, grain boundary, and hetero-deformation induced hardening/strengthening are the dominant strengthening mechanisms affecting mechanical properties.