Microstructure evolution of Mg-10Gd-3Y-1.2Zn-0.4Zr alloy during heat-treatment at 773Â K

Microstructure evolution of Mg-10Gd-3Y-1.2Zn-0.4Zr alloy during high temperature heat-treatment at 773 K in the time range 12-72 h is investigated. Addition of 1.2% Zn increases the amount of Mg5(Gd,Y,Zn) eutectic compounds and form of basal plane stacking faults (SF) of Mg crystal in the as-cast alloy. During heat-treatment at 773 K, parts of eutectic compounds dissolve gradually into the matrix with time prolonged, a new 14H type of LPSO and fcc structured cuboid-shaped RE-rich phases come into being. Two kinds of morphologies of these 14H LPSO phases: block-shaped and fine lamellar-shaped are generated through transformation from Mg5(Gd,Y,Zn) eutectic compounds by heat treatment control.