Crystallography of recently developed grain refiners for Mg–Al alloys

Abstract

The grain refinement potency of some recently reported grain refiners for Mg–Al based casting alloys, including TiC, TiN, SiC and TiB₂, was investigated from a crystallographic viewpoint using the edge-to-edge matching model. The results show that TiB₂ is more likely to form an energetically favourable orientation relationship with the Mg matrix, and it is predicted that TiB₂ should have the best grain refinement efficiency. The other three compounds may also serve as heterogeneous nucleation sites, but are not likely to be as effective as TiB₂. The present analysis provides a better rationale of the superior grain refinement performance of TiB₂ compared with SiC.

Acknowledgement

The authors are very grateful to the Australian Research Council for funding support.