Heat treatment, microstructure and mechanical properties of a Mg-Gd-Y alloy grain-refined by Al additions

The effect of additions of 0.5-1 wt% Al on grain refinement, heat treatment and mechanical properties of Mg-10Gd-3Y (wt%) alloy has been investigated. The additions of 0.6-1 wt% Al showed a dramatic grain refinement effect, which is associated with the formation of the Al2(Gd0.5Y0.5) particles that act as nucleants for α-Mg grains. Compared to the Zr refined counterpart, the Al refined alloy needed to be solution treated at a higher temperature to dissolve the majority of the intermetallic particles. Subsequent ageing at low temperatures led to pronounced precipitation hardening and consequently a large improvement in strength. In the peak-aged condition, the strength of the Al refined alloy is comparable to that of the Zr refined counterpart.