Microstructure Evolution and Tensile Behavior of Dissimilar Friction Stir-Welded Pure Copper and Dual-Phase Brass

6-mm-thick pure copper and dual-phase brass plates were joined using friction stir welding (FSW). The role of plate location prior to welding and the tool rotational speed on the microstructure evolution was evaluated and correlated to the tensile properties of the joint. All the joints with copper on advancing side produced defects. Typical zones commonly found in FSW joints were observed. TMAZ was not found on the copper side, and no coarsening of grains was noticed in the HAZ on the brass side. The microstructure of the weld zone was heterogeneous and grouped into three categories. The plate position and the tool rotational speed influenced the material flow and the formation of different structures. The weld zone was further characterized by ultra-fine grains, dislocations and annealing twins. The hardness across the weld zone was varying considerably. The process parameter had an opposite effect on the hardness of brass and copper portion of the weld zone. The joints with brass on advancing side showed higher tensile strength. The fracture location and surfaces were further reported.