Effect of nickel interlayer on laser welding of copper/titanium dissimilar metal joint

Abstract

Cu/Ti dissimilar metal welding components have significant potential applications in aerospace, nuclear industries, and other fields. To achieve a robust connection between titanium (TA2) and copper (T2), this study conducted laser-welding experiments using nickel as an intermediate layer. The influence of a nickel intermediate layer on the joint formation, microstructure, mechanical properties, melting, and element diffusion behavior were investigated. The results revealed that without the addition of a nickel intermediate layer, when the laser beam was biased toward the titanium side during welding, a 17 μm thick layer of intermetallic compounds formed in the copper-side weld region. In this area, a notable concentration of fragile Ti–Cu intermetallic compounds forms, rendering it the weakest point in the joint. As a consequence, the ultimate tensile strength of the joint measures at 131 MPa, which is roughly 55 % of the tensile strength of the copper base material. The introduction of a nickel intermediate layer led to a change in the microstructure of the fusion zone, with Cu–Ti intermetallic compounds dispersed within, preventing the formation of brittle Ti–Cu phases at the copper interface. The addition of the nickel interlayer increased the tensile strength of the TA2-T2 joint to 224 MPa, which is approximately 94 % that of the copper parent material, and the joint exhibited ductile fracture behavior in the copper parent material's heat-affected zone.