Effect of extrusion temperature and speed on texture evolution in Mg-Zn-Gd alloy and their correlation with mechanical properties

Abstract

It is generally believed that the addition of rare earth (RE) elements can modify the texture distribution to form a distinct RE texture, which is typically weaker and more dispersed than conventional textures. In this study, we systematically investigated the influence of extrusion temperature and speed synergy on grain boundary segregation and texture evolution in Mg-2Zn-1Gd (wt.%) alloy. Further investigation using Electron Backscattered Diffraction (EBSD) and Energy Dispersive Spectroscopy (EDS) in Scanning transmission electron microscopy mode (STEM-EDS) revealed that rare earth magnesium alloys (Mg-RE alloys) do not invariably result in the formation of RE textures, that is under low-temperature and low-speed conditions, Zn/Gd co-segregation dominates RE texture formation by increasing the critical strain for dynamic recrystallization and promoting the nucleation of twins and shear bands. Under high-temperature and high-speed conditions, an imbalance in segregation kinetics (grain boundary migration rate > solute diffusion rate) activates basal slip. This basal slip is activated within recrystallized grains to accommodate imposed strain, contributing to the development of a strong basal texture. In addition, the effect of microstructure evolution with extrusion parameters on mechanical properties of Mg-2Zn-1Gd rods are also systematically investigated, and a numerical calculation are conducted to determine the mechanism on the effect of texture evolution on mechanical properties.