Cryogenic rapid quenching simultaneously enhances the strength and ductility of steel–Aluminum composite plates

Roll-bonded steel–aluminum composite plates exhibit poor plasticity due to work hardening induced by severe plastic deformation. In this study, the mechanisms for improving the plasticity of steel–aluminum composite plates were investigated through liquid-nitrogen quenching from both material science and mechanical perspectives. From a materials science perspective, rapid cryogenic quenching forms numerous dislocation walls and cells within the Al matrix. These dislocation configurations effectively limit dislocation movement during tensile deformation. Additionally, the difference in thermal expansion properties between the steel and aluminum matrices generate significant microstrain near the interface, enhancing the back stress-induced strengthening effect. From a mechanical perspective, rapid cryogenic quenching increases the hardness and tensile strength of the aluminum matrix. A stronger aluminum matrix restricts the deformation of the steel matrix during tensile loading, delaying the onset of necking in the steel matrix. Additionally, the significant hardening of the aluminum matrix can cause the tensile specimen to bend, creating two potential necking points that divide the tensile strain, thereby significantly increasing the pre-necking deformation of the composite plate. Compared with untreated specimens, the tensile elongation and tensile strength of the specimens treated with rapid cryogenic quenching increased by 49.1% and 10.8%, respectively. This study provides a novel approach to simultaneously enhance the strength and plasticity of composite plates.