A Study on the Microstructural Evolution, Interfacial Diffusion and Mechanical Properties of Ultra-thin Stainless Steel–Copper Composites Fabricated by Roll Bonding

Systematic study on the microstructural evolution, interfacial diffusion and mechanical properties of ultra-thin stainless steel–copper composites (50 µm) after annealing treatment was conducted in the present study. The results show that the as-received specimen exhibits low elongation (0.031) as well as high strength (891.346 MPa) by work hardening, thus requires heat treatment to improve the plasticity. With the increase of annealing temperature from 700 to 1000 °C, the dislocation/grain boundary strengthening is weakened while the surface grains which exhibit fewer constraints is increasing, resulting in lower strength. Moreover, a uniform and refined microstructure with high recrystallization rate is formed inside stainless steel and copper matrixes for the specimens annealed at 900 °C, thereby improving the plasticity of ultra-thin stainless steel–copper composites. Additionally, an obvious strain gradient exists at the interface of ultra-thin stainless steel–copper composites, and the interdiffusion process between stainless steel and copper matrixes is primarily governed by the diffusion of Cu atoms. The influence of diffusion layer thickness on the strength of ultra-thin stainless steel–copper composites is negligible. Overall, an optimal annealing temperature of 900 °C is obtained with the improved plasticity of ultra-thin stainless steel–copper composites.

Graphical Abstract