Effect of ageing treatment on the microstructures and mechanical properties of the extruded Mg–7Y–4Gd–1.5Zn–0.4Zr alloy

Microstructures and mechanical properties of Mg–7Y–4Gd–1.5Zn–0.4Zr alloy in the as-cast, as-extruded and peak-aged conditions have been investigated by using optical microscope, scanning electron microscope, X-ray diffraction and transmission electron microscope. The results show that optimal mechanical properties of this alloy are obtained when it was aged at 220 °C. The values of the ultimate tensile strength and yield tensile strength are 418 and 320 MPa, respectively. The age hardening response decreases with increasing ageing temperature because the β′ phase gets coarse as ageing temperature increases.