The Investigation on the Dissimilar Material Overlapping Region via Friction Stir Lap Welding of Copper and Titanium

Abstract

The technological innovation of joint method for dissimilar metals of titanium (Ti) and copper (Cu) still stays in demand. The promising joining method of friction stir lap welding was successfully introduced to produce the defect-free and high-performance lap joints of dissimilar Cu and Ti sheets. After process parameter optimization, the macro/micro-structures, and mechanical tensile properties of the lap joints were carefully analyzed. The formation mechanisms of the Cu/Ti alternate band structure were discussed in detail, as the results of utilizing a special Cutting Pin for promoting Cu/Ti mixing and transferring and limiting the evident formation of Cu-Ti inter-metallic compound phases in the overlapping region, with the composite-like structure playing a so-called mechanical locking effect on the Cu/Ti lap joints. The strengthening effect was also provided by the metallurgical bonding at the Cu/Ti band interfaces without cracking in micro scale. The fracture resistant strength of the joint reached 95% of that of the used parent copper.