Influence of Sb on microstructure of 20 Mg2Si/Al-Si composites has been described. The results show that with the increase of Sb addition

primary Mg

Si phase is remarkably refined

in which chi-nese script or dendritic Mg2 Si phase is converted into uniformly distributed fine particle

and the volume fraction of Mg2Si phase is slightly increased. The optimum particle appearance and refinement can be obtained with about 0. 1% Sb addition

where the size of Mg2Si phase is refined to 25 μm from 52μm. However

excessive Sb content can results in coarsening par-ticle

which means the excessive Sb can detriment the refinement effects. The refinement of Mg2Si phase can be attributed to heterogeneous nucleation resulting from AlSb compound

meanwhile

Sb can decrease liquidus temperature and molten surface tension

which refines the Mg2Si phase to a certain degree too.