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

Abstract

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.