Effect of annealing temperature on microstructure and properties of stainless steel/copper composite strips

Stainless steel/copper composite strips (SSCC) were fabricated using stacked rolling followed by finishing processes. These SSCC underwent annealing at temperatures of 300℃, 400℃, 500℃, and 600℃ for a duration of one hour. The deformation characteristics of the composite strips during rolling were thoroughly analyzed. In addition, investigations were carried out on their mechanical properties and microstructural evolution. The results indicate that as the annealing temperature increases, the tensile strength of the SSCC decreases slightly, while the elongation increases significantly. Initially, the peel strength of the rolled SSCC is the lowest, but it increases progressively as the annealing temperature rises. At the annealing temperature of 600°C, the peel strength of the composite strip reaches its maximum value of 7.1 N/mm. Significant interface delamination is observed during the bending process of the rolled SSCC. However, at the annealing temperature of 600°C, interface delamination is absent in the SSCC, resulting in optimal bonding quality. The rolled SSCC exhibits prominent defects, including cracks and holes at the bonding interface. In contrast, annealing significantly reduces both the number and size of these cracks and holes, indicating improved interface bonding quality. As the annealing temperature increases from 300°C to 600°C, the grain size of copper increases from 8.45μm to 28.5μm, and the proportion of low-angle grain boundaries (LAGBs) rises from 1.2% to 3.7%. Additionally, a significant number of 60° grain boundaries is observed, suggesting the formation of numerous annealing twins. In the stainless steel (SS) layer, martensitic transformation occurs due to rolling. The austenite grains in the SS progressively enlarge, while the martensite grains decrease accordingly as the annealing temperature increases.