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 degrees 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) over bar 1}-{1 0 (1) over bar 2} type, possessing the misorientation of 37.5 degrees 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 beta precipitates with irregular shapes are observed to form firstly on twin boundaries. Then the formation of rectangular beta' precipitates proceeds in the Mg matrix. The morphology of the beta' 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. Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved