Effect on Zn on Microstructures and Mechanical Properties of Mg–Gd–Y–Zn LPSO Alloys

In this study, the microstructures and mechanical properties of Mg–1Gd–1Y–xZn alloys (x = 0.2, 0.4, 0.6, and 0.8) were investigated. Microstructural evolution was tracked during the process of casting, homogenization, and extrusion. Long-period stacking-ordered (LPSO) and β phases were formed in the as-cast alloys. The volume fraction of the LPSO phase increased with increasing Zn content, whereas that of the β phase decreased. Although the homogenization dissolved the β phase into the Mg matrix, there was no significant change in the volume fraction of the LPSO phases. Increasing the Zn content led to a slight reduction in grain size and a simultaneous strengthening of texture. The Mg–1Gd–1Y–0.2Zn alloy possessed a high density of fine LPSO phases and excellent reinforcement capacity, thereby exhibiting excellent mechanical properties at room temperature. In addition, the low volume fraction of the LPSO phases in this alloy led to suppressed yield asymmetry.