The effect of aluminium content on the eutectic morphology of high pressure die cast magnesium–aluminium alloys

Increasing aluminium levels in high pressure die cast Mg–Al alloys results in an increase in the volume fraction of eutectic Mg17Al12 with a change in its morphology from fully divorced through to fibrous. Comparison with work undertaken at slower cooling rates shows that the primary α-Mg morphology has a more significant effect on the eutectic Mg17Al12 morphology than cooling rate alone. The morphology of α-Mg is controlled by the number of nucleation events and the cooling rate.