Study on residual stress distribution of Al/Cu dissimilar metal joint manufactured by electromagnetic pulse welding

Abstract

Electromagnetic pulse welding (EMPW) is a cold-welding technology to connect materials by driving the flyer plate with electromagnetic force to impact the target plate at high speed and it has been adopted to join dissimilar metals. In the present study, a dissimilar metal (2024 aluminum alloy and pure copper) joint was prepared with the EMPW. The contour method was used to get the full map of longitudinal stress distribution in the joint. The stress variation across the thickness was analyzed. The results show that the tensile stress appears at the side of aluminum alloy, and compressive stress occurs at the side of pure copper. The peak tensile stress (260 MPa) appears in the aluminum alloy plate at the location with 0.2 mm from the welding interface. The peak compressive stress in the copper plate is −254 MPa, occurring at the location with 0.1 mm from the welding interface. Within 0.3 mm, the peak tensile stress changes to the peak compressive stress, indicating a steep stress gradient across the EMPW joint. Instantaneous temperature variation, the difference between the coefficient of thermal expansion of aluminum and copper, and the metal-plastic flow induced by impact within the thin welding zone cause the steep stress gradient.