Microstructure and Mechanical Properties of an Extruded Mg-1.58Zn-0.52Gd Alloy

Mg-1.58Zn-0.52Gd (wt%) alloy was indirectly extruded at different temperatures and the resulting microstructure, texture and mechanical properties were investigated. The alloy extruded at 350 degrees C exhibited a typical bimodal microstructure, consisting of fine dynamically recrystallized (DRXed) grains of similar to 3.1 mu m and coarse unDRXed grains elongated along the ED with many fine spherical Mg3Zn3Gd2 phase, and a strong [10 (1) over bar0] fiber texture, thereby resulting in high yield strength of 283 MPa and low elongation of 10.0%. With increasing extrusion temperature, the yield strength gradually decreased mainly due to increased DRXed grain size from the Hall-Petch relation, and the elongation increased due to the weakened extrusion texture and increased DRX fraction, suppressing crack initiation at twins in coarse unDRXed grains. As a result, the alloy extruded at 400 degrees C showed yield strength of 161 MPa and elongation of 24.7%.