Gadolinium solubility and precipitate identification in Mg-Gd binary alloy

Gadolinium (Gd) solubility in magnesium (Mg) matrix and precipitate composition in Mg-Gd binary alloys were investigated. The alloys containing different Gd contents (10 wt.%-35 wt.%) were employed to identify Gd solubility after annealing at different temperatures. It was confirmed that the maximum Gd solubility was 22.8 wt.% at 550 degrees C based on the regression analysis method. Mg5+xGd (0<x<2) and Mg3Gd precipitates coexisted in all investigated alloys owing to the strong component segregation during solidification. The fraction of Mg5+xGd (0<x<2) was decreased with the increment of annealing temperature and time. In contrast, Mg3Gd precipitate could not be eliminated even when being annealed at 550 degrees C. This thermal stable precipitate played a significant role in mechanical properties. Therefore, it is very necessary to consider the effect of Mg3Gd precipitate on properties of Mg-Gd based alloys in future.