Inhibition of Grain Growth by a Ce-rich Precipitate During the Annealing of Spray-Casted Magnesium Alloy

The grain refinement and thermal stability behavior of a spray-casted AZ91D magnesium alloy were investigated with the addition of 0.75 wt% Ce. The results showed that the adoption of non-equilibrium solidification leads to remarkable grain refinement and the formation of a supersaturated solid solution, which suppresses the needle-like Al(11)Ce(3) phase with a low cooling rate. After annealing at 420 °C, the grain morphology of rapidly solidified AZ91D+0.75Ce alloy changed from a granular to polygonal shape. Moreover, Mg(12)Ce particles precipitated and distributed homogeneously, which played an important role in grain boundary pinning at an elevated temperature. Consequently, the grain growth occurring during the isothermal annealing stage could be suppressed and the resultant grain size varied slightly, as did for the time, which increased from 2 h to 8 h.