Comparison of microstructure in Mg–10Y–5Gd–0.5Zr and Mg–10Y–5Gd–2Zn–0.5Zr alloys by conventional casting

Mg–10 wt.%Y–5 wt.%Gd–0.5 wt.%Zr (WG105) and Mg–10 wt.%Y–5 wt.%Gd–2 wt.%Zn–0.5 wt.%Zr (WGZ1052) alloys are processed via a conventional casting method. By adding 2 wt.% Zn into WG105 alloy, the microstructure changes remarkably. It can be seen that a long-period stacking order structure (LPSO) is formed. The lattice is a 6H′-type (ABCBCB′) which is a distorted stacking order from an ideal hexagonal lattice of 6H-type (ABCBCB). It also can be seen that the growth of some 6H′-phases stop growing at the grain interior and others run through the whole grain. Furthermore, in different grains the growth of 6H′-phase takes on different orientations, but in the same grains the orientation is uniform.