Heterogeneous nucleation in Mg–Zr alloy under die casting condition

• The heterogeneous nucleation in a die casting Mg–Zr alloy was investigated.
• The nucleation efficiency of Zr particles was calculated as 48.78%.
• Various nucleation interfaces were investigated by HRTEM.
• The nucleation behaviour was independent on any crystallography orientation.
• A heterogeneous nucleation mechanism was proposed in die casting Mg–Zr alloy.

Heterogeneous nucleation behaviour was studied in die casting Mg–Zr alloy. It was found that up to 48.78% Zr particles could be used as nuclei and the nucleation occurred on curved and faceted interfaces. It meant that the size effect of nuclei in Mg–Zr alloy was insignificant, and this nucleation behaviour was independent on any crystallography orientation. Therefore, a large range of Zr nuclei could be activated simultaneously under the large undercooling through the delayed recalescence resulting in a very high nucleation efficiency.