Effect of Er content on mechanical properties and microstructural evolution of highly-alloyed Mg-10Gd-5Y alloy

The influence of Er content on mechanical properties and microstructural evolution of highly-alloyed Mg-10Gd-5Y-xEr alloys (x = 0, 2, 3.5, 5, and 6.5 wt%) are investigated. The tensile strength is found to increase monotonously with increasing Er content, while the ductility is slightly reduced due to the increased formation of block precipitates. The maximum tensile yield strength and ultimate tensile strength are achieved to be 296 MPa and 374 MPa, respectively, within the studied concertation interval. Solid solution strengthening and grain refinement are demonstrated to dominate the increase of tensile yield strength upon Er content, where the latter becomes the primary strengthening mechanism at relatively high Er contents (> 5 wt%). It is closely related to the consumption of Gd and Y in solid solution by the precipitation of Mg24RE5 particles and alloying element segregation at grain boundary. The significant reduced grain size of dynamic recrystallized grains upon Er content is attributed to the promoted dynamic recrystallization via particle stimulation nucleation and the retardant grain growth emerging from the drag and pinning effect of alloying element segregation and nano-precipitates at grain boundary.