Effects of Al-3Ti-3B master alloy on grain refinement of AZ31 magnesium alloy were observed by OM （optical microscope）

XRD （X-ray diffraction）

SEM （scanning electron microscope） and EPMA. The results reveal that coarse dendrite is transformed into uniform equiaxed grain in the as-cast AZ31 alloy with proper Al-3Ti-3B master alloy. Desirable refining effects can be observed in the alloy with 0.4% Al-3Ti-3B alloy. Average grain size in solid solution treated AZ31 alloy is refined from 300 μm to 50 μm. Grain refinement is mainly controlled by creation of TiB2 and AlB2 particles as heterogeneous nuclei

and aggravation of TiB2 phase at the grain boundary can further restrain the growth of the primary Mg phase.