Effect of Ca addition on grain refinement of Mg–9Li–1Al alloy

The as-cast and as-extruded Mg–9Li–1Al–xCa alloys (x = 0, 0.2; wt%) were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2. The microstructures of the as-cast and as-extruded Mg–9Li–1Al–xCa alloys were observed to investigate the effect of calcium (Ca) element on the Mg–9Li–1Al (LA91) alloy, and the crystallographic calculations between Al2Ca and the matrix (α-Mg and β-Li phases) were examined on the basis of the edge-to-edge matching model. The experimental results indicate that the addition of 0.2 wt% Ca into LA91 alloy reduce the size of the α-Mg phases in the as-cast alloy and that of β-Li phases in the as-extruded alloy due to the Al2Ca particles distributed inside the matrix. Crystallographic calculation results suggested that there is a good crystallographic matching between the matrix and Al2Ca, which confirmed that Al2Ca particles can act as a heterogeneous nucleation site for both α-Mg and β-Li phases and were effective grain refiners for LA91 alloy.