Grain refinement of Ca addition in a twin-roll-cast Mg–3Al–1Zn alloy

Addition of 0.08 wt% Ca into AZ31 melts significantly reduces the average grain size of thin strips produced by twin-roll-cast to 30 μm from 100 μm. Like Zr, due to the high chemical activity, the Ca added into the melts reacts with Al and forms Al2Ca intermetallic compound. X-ray diffraction result approves the existence of Al2Ca in the thin strips, which formed in the melts. Crystallographic examination of relationship between Al2Ca and Mg using the edge-to-edge matching model indicates that Al2Ca particles are effective inoculants for heterogeneous nucleation of Mg. It is considered that Al2Ca is a potential and effective grain refiner for Mg alloys and the grain refinement through addition of Ca in the AZ31 alloy is attributed to the inoculation effect of Al2Ca particles formed in the melts.