A new perspective on tensile yield plateau formation in extruded Mg-4.83Gd-2.36Nd-0.21Zr alloy

The occurrence of the tensile yield plateau in Mg alloys is relatively rare and its underlying reasons have been controversial. In this study, we systematically investigated the deformation mechanism of an extruded Mg-4.83Gd-2.36Nd-0.21Zr alloy, which exhibited an obvious tensile yield plateau. Quasi-in-situ EBSD analysis revealed that basal slip was the predominant mechanism in the tensile yield stage, which was attributed to the weak rare earth texture that facilitated basal slip activation and the fine recrystallized grains that suppressed twinning. The yield drop resulted from the combined effects of the easy activation of basal slip and the dislocation pinning by solute atoms. Additionally, the random distribution of grain orientations, high grain boundary misorientation angles (GBMA), and small grain sizes hindered intergranular deformation transfer between neighboring grains. The weak deformation transfer contributed to the formation of yield point elongation. This work underscores the role of texture, grain orientations, and GBMA in determining the yield plateau, offering a new perspective on yield plateau formation in Mg alloys.