Effect of Zn content on the microstructure and mechanical properties of Mg-Gd-Y-Zr alloys

The effect of Zn content on the microstructure of hot extruded Mg-10.5Gd-5Y-0.5Zr (wt%) alloys was investigated. The results show that with the increasing of Zn content from 0 to 1.8 wt%, grain size of the alloys gradually decreases from 7.1 to 2.7 mu m. Although the grain sizes are refined significantly, the textures of these alloys only change mildly. With the averaged Schmid factor for basal slip remaining nearly the same, percentage of grains with higher Schmid factor values decreases with the addition of Zn. At the same time, LPSO phases in various morphologies appear due to the addition of Zn. At relatively low content of Zn, the LPSO phase adopts a thin plate-shaped morphology and embeds itself inside the grains; with the Zn content increased to 1.2 wt%, block-shaped LPSO phase starts to form and its volume fraction increases with the Zn content. Strength of these alloys are gradually increased while ductility decreased, and the contributing factors are discussed based on the microstructures mentioned above.