Twinning and dynamic precipitation upon hot compression of a Mg−Gd−Y−Nd−Zr alloy

The microstructure evolution in Mg–8Gd–2Y–1Nd–0.3Zn–0.6Zr alloy subjected to hot compression at 350 °C and the strain rate of 0.5 s−1 was systematically investigated. Twinning and dynamic precipitation are two characteristic processes during compressive deformation. Crystallographic analysis indicates that the majority of deformation twins are of the {1 0 1¯ 1}-{1 0 1¯ 2} type, possessing the misorientation of 37.5° from parent grain about the c-axis. With strain accumulation, the twin–twin intersections lead to grain fragmentation of the original grains. Extensive dynamic precipitation is observed in the alloy. The β precipitates with irregular shapes are observed to form firstly on twin boundaries. Then the formation of rectangular β′ precipitates proceeds in the Mg matrix. The morphology of the β′ precipitates differs from that of the same phase obtained by solution and ageing treatment (i.e. T6 heat treatment), but their orientation relationships with Mg matrix keep consistent.

► {1 0 1¯ 1}-{1 0 1¯ 2} double twinning is dominate supplementary deformation mechanism.
► Dynamic precipitation remarkably inhibited recrystallization.
► Precipitate morphology differs from that of the same phase obtained by T6 treatment.