Effect of Annealing Temperature on Morphology of LPSO Phase in Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr Alloy

The extruded Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr(wt%) alloy was employed as the starting material. Optical microscope and transmission electron microscope were applied to investigate the effects of annealing temperature on the morphology of LPSO phase. The results show that annealing temperature significantly affects the microstructure, morphology, size and distribution of LPSO phase. The alloy is full of dense metastable LPSO phases after annealed at 350℃. While with the temperature increase to 450℃ and 500℃, the LPSO phase transfers into a stable 14H structure. Meanwhile, the LPSO phase becomes thicker in <0001>αdirection and shorter in <1010>αdirection, and the distribution of LPSO phase becomes sparser.The LPSO phase morphological differences are attributed to differences in solidity and diffusion behavior of solute atoms at different temperatures.