Precipitates formed in a Mg–7Y–4Gd–0.5Zn–0.4Zr alloy during isothermal ageing at 250 °C

The ageing behavior of an extruded Mg–7Y–4Gd–0.5Zn–0.4Zr alloy during ageing at 250 °C has been investigated. Two types of phases have been observed during the ageing process. One is a lamellar phase with a 14H long periodic stacking structure, the other is the β′ phase with an ellipsoidal morphology. The increased mechanical properties of the peak-aged alloy are mainly ascribed to the presence of both of these phases at peak hardness.