Microstructure, texture, and mechanical properties of friction stir spot welded rare-earth containing ZEK100 magnesium alloy sheets

The effect of friction stir spot welding process parameters on the microstructure, texture, and mechanical properties of ZEK100 (Mg-1.0 wt% Zn-0.5 wt% RE-0.5 wt% Zr) Mg alloy was investigated. Lap-shear joints were prepared using two different tool rotational speeds (1500 and 2250 rpm) and three different shoulder plunge depths (0.0, 0.2, 0.6 mm). Microstructure analysis revealed significant grain refinement in the stir zone, when compared to the base material. Electron backscatter diffraction analysis revealed a strong texture development in the keyhole periphery and adjacent regions despite the presence of RE-elements, however, no significant texture variation was observed within the process parameters. These results suggest that the ultimate failure of the weld is more attributed to macroscopic features such as the bond width and upper sheet thickness rather than texture development.