Hot compression deformation behavior of Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr alloy

High temperature deformation behavior of Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr alloy was investigated by hot compression tests on a Gleeble-1500 machine at the temperature range of 623-803 K,strain rates between 0.005 s-1 and 5 s-1.The results show that flow stress of the Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr alloy increases quickly with increasing strain and reaches a peak,then decreases to a steady value.The steady and peak stress significantly decreases with increase of deformation temperature and decrease of strain rate.A flow stress model of the Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr alloy for high temperature deformation was established based on the Arrhenius equations.At deformation temperature of 723 K and strain rate of 0.05 s-1,the necklace microstructure,which is characterized by large grains encircled by fine grains,scatters over the deformation regions of sample,and cavities are observed at intersections of grains.The temperature about 773 K is suggested for hot deformation of this alloy.