Effect of element composition on microstructure pattern of Mg-RE alloys

The microstructure of as cast Mg-RE (Mg-Gd, Mg-Y, Mg-Gd-Y and Mg-Gd-Y-Nd) alloys and that after heat treatment were investigated.The results show that the primary solidified precipitated phases of both Mg-Gd and Mg-Y binary alloy were coarse aberration eutectic microstructure pattern.For Mg-Gd-Y ternary alloy, a small amount of lamellar eutectic microstructure was formed while that mainly was coarse coefficient eutectic microstructure in matrix.In Mg-Gd-Y-Nd quaternary alloy, the as-cast microstructure was composed of α-Mg matrix and α-Mg+Mg 5 (Gd, Y, Nd) phase which had lamellar structure on grain boundaries.Compared with Mg-Gd, Mg-Y, Mg-Gd-Y alloy, the remaining second phase particles in Mg-Gd-Y-Nd alloy was more dispersed after heat treatment.