Effects of Sm element addition on the workability and microstructure evolution of Mg-Gd-Y-Zr alloy during hot deformation

Abstract

A new Mg-5.5Gd-3Y-1Sm-0.5Zr (1Sm) alloy was developed. The deformation behavior and microstructure evolution of the Mg-Gd-Y-(Sm)-Zr alloys during hot compression were investigated systematically. The effects of Sm element addition on the workability and dynamic recrystallization (DRX) behavior of the Mg-5.5Gd-3Y-0.5Zr (0Sm) alloy was revealed. Sm element will increase the thermal activation energy and reduce the discontinuous dynamic recrystallization (DDRX) at 350 °C and 400 °C. The Mg5(Gd)-type phases are precipitated dynamically in the Mg matrix during low-temperature deformation process, and recrystallization occurs near the precipitated phase particles. At 450 °C and 500 °C, the continuous dynamic recrystallization (CDRX) is more prone to occur in the 1Sm alloy due to the high accumulation of misorientation angles in the initial coarse grains, so the DRX fraction of 1Sm alloy is higher than that of the 0Sm alloy. Furthermore, it is found that Sm element can weaken the basal texture. The intensity of the basal texture of the DRX grains of 1Sm alloy is lower than that of the 0Sm alloy at any temperatures. Based on the processing map, the optimum hot forming parameters of the 1Sm alloy is defined as temperature range 450–500 °C and strain rate range 0.01–0.1 s −1.