Revealing the microstructure characteristics, deformation behavior and mechanical properties of weakly textured Mg–Y-Nd-Gd-Zr alloy FSW joints

In this work, friction stir welding (FSW) was performed on Mg–Y-Nd-Gd-Zr plate using two different welding parameters: 100 mm/min-1600 rpm and 100 mm/min-1000 rpm. The mechanical properties, deformation characteristic and microstructure of the FSW joints were thoroughly explored. Microstructure analysis revealed a significant refinement in the nugget zone (NZ), with original precipitates being considerably remelted into the matrix. Moreover, the micro-texture in NZ showed symmetrical distribution features, with the highest texture intensity at the NZ-side of the advancing side. Tensile results displayed that the strength of both joints exceeded 95% of the base material (BM), while their elongation was markedly inferior to the BM, with values of 13.8% and 12.2%, respectively. The higher joint connection strength was attributed to the combined effects of dislocation strengthening, grain refinement, precipitation phase re-dissolution softening, and favorable orientation of basal slip near the weld interface. However, the significantly reduced elongation of the two joints resulted from strain localization on the NZ-side with a high Schmid factor (SF) value. Additionally, the fracture occurred adjacent to the NZ-side of these two joints owing to its high SF value, relatively coarse grains, and distinct interface characteristics. This work can provide new reference and understanding for the FSW study of wrought Mg rare earth alloys.