Effects of the Extrusion Temperature on Microstructure, Texture Evolution and Mechanical Properties of Extruded Mg–2.49Nd–1.82Gd–0.19Zn–0.4Zr Alloy

Microstructure, texture evolution and mechanical properties of extruded Mg–2.49Nd–1.82Gd –0.19Zn–0.4Zr alloy were investigated at extrusion temperatures of 260 °C, 280 °C, 300 °C and 320 °C, with an extrusion ratio of 15 and RAM speed of 3 mm s⁻¹, respectively. The results indicated that the coarse grains of homogenized billets were substantially refined after the extrusion process, which was caused by the refinement of dynamically recrystallization (DRX) and the pinning effect of precipitated Mg₅Gd and Mg₁₂(Nd, Gd) particles. The grain size decreased gradually when the extrusion temperature increased from 260 to 280 and 300°C, and then coarsened slightly once the extrusion temperature further increased to 320 °C. Moreover, the DRX process was promoted with the increasing extrusion temperature, and a completely DRX microstructure could be obtained when the extrusion temperature up to 300 °C. The room temperature tensile and compressive yield strength increased when the temperature increased from 260 to 300 °C and then decreased at 320 °C. All extruded alloys exhibited an extremely low tension–compression yield asymmetry, which was mainly attributed to the rare earth (RE) texture component as well as the fine microstructure developed during the extrusion process.