Tracing the evolution of microstructures, mechanical properties and corrosion behaviors of as-rolled Mg-Y and Mg-Y-Ca alloys during heat treatment

This work investigated the evolution of microstructures, mechanical properties and corrosion behaviors of as-rolled Mg-3Y and Mg-3Y-0.4Ca (wt%) alloys during heat treatment. The samples annealed at 350 ℃ has smaller grain sizes than the as-rolled samples because of static recrystallization, and the grain size increased with increasing annealing temperature. The minor addition of Ca promoted continuous dynamic recrystallization mechanism and decreased the grain size to some extent. For the as-rolled samples, the contribution of dislocation strengthening to the strength was ∼50 %, whereas this contribution was negligible for the annealed samples. As the annealing temperature increased, the contribution of grain boundary strengthening continuously decreased. In contrast, the contribution of solution strengthening gradually increased, and the addition of Ca increased the mechanical strength by increasing the contributions of grain boundary strengthening and solution strengthening. Compared with that of the as-rolled samples, the corrosion resistance of both the Mg-Y and Mg-Y-Ca samples obviously increased after annealing, and the corrosion resistance increased as the annealing temperature increased. In addition, the addition of Ca could enhance corrosion resistance by reducing the heterogeneity of overall potentials and increasing the compactness of corrosion product films.