Investigation of mechanical and corrosion properties of ultrasonically welded aluminum-copper joints under extreme environmental conditions

As a solid-state joining process, ultrasonic welding (USW) offers significant advantages for creating robust aluminum-copper joints. This study investigates the mechanical and corrosion properties of ultrasonically welded Al–Cu lap joints under extreme environmental conditions. The properties were evaluated at high temperature (100 ℃), various low temperatures (− 20 ℃, − 30 ℃, and − 40 ℃) and in a salt spray corrosion environment (24 h, 48 h, 72 h, and 96 h). Using identical welding parameters, the changes in mechanical properties and failure forms were examined and clarified. Results showed that at 100 ℃, shear strength decreased slightly. However, the failure displacement declined significantly, indicating poor resistance to deformation and fracture. At low temperatures, joint tensile strength degraded with decreasing temperature, yet electrical conductivity remained good. Furthermore, mechanical properties significantly degraded in the salt spray environment, with the weld strength coefficient dropping to 82.12% after 96 h of corrosion. The base plate corroded with increasing salt spray exposure, leading to the subsequent penetration of corrosive liquid into the weld. This corrosion then extended to the weld edge, exacerbating the electrochemical corrosion rate of the joint.