Effect of extrusion temperature on microstructure and mechanical properties of a low-rare-earth Mg-Gd-Sm-Zr alloy

Optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), tensile tests, and Vickers hardness measurements were used to investigate the effects of extrusion temperatures (380, 400, and 420 °C) on the microstructure, texture, and mechanical properties of the Mg-3.68Gd-2.05Sm-0.52Zr alloy. Results show that the as-cast alloy has an average grain size of 11.13 μm, with few second-phase particles near grain boundaries. Hot extrusion fragments these particles and significantly refines grains. The alloy extruded at 400 °C achieves optimal properties: yield strength of 247.7 MPa, ultimate tensile strength of 311.7 MPa, and elongation of 26.5%. Mechanical properties are synergistically controlled by the competitive coupling of multiple strengthening mechanisms.