Microstructural evolution and aging behavior of Mg-4.5Y-2.5Nd-1.0Gd-0.5Zr alloys with different Zn additions

Microstructures and mechanical properties of Mg-4.5 Y-2.5 Nd-1.0 Gd-0.5 Zr-xZn(x=0,0.5,1.0,and 1.5;wt%)alloys under as-cast and peak-aged states were investigated in this work.The results indicate that the intermetallic phase components are closely dependent on Zn content.Under as-cast state,the dominant eutectic phase is Mg5 RE in the alloys with 0 wt%and 0.5 wt%Zn additions while Mg5 RE,18 R-and 14 H-LPSO(long period stacking ordered)phases in the alloys with 1.0 wt%and1.5 wt%Zn additions.After solution and peak-aging,the highest strength and hardness were obtained on the alloy with 0.5 wt%Zn addition.Transmission electron microscopy(TEM)characterizations revealed that there are denser and finer precipitates on basal(β’)and prismatic(γ’)planes,respectively.Therefore,the excellent mechanical performance of the alloy with 0.5 wt%Zn addition is mainly due to precipitation strengthening and grain boundary strengthening.