Effect of Gd content on microstructure and mechanical properties of Mg-Gd-Y-Zr alloys under peak-aged condition

The current study investigates the effects of different Gd contents (3-12 wt%) on the microstructure, age hardening response and mechanical properties of the Mg-xGd-3Y-0.5Zr alloys. The age hardening response of the alloy increased with increasing Gd content, and tensile strength of the alloy improved with addition of Gd up to 10 wt%. The Mg-10Gd-3Y-0.5Zr alloy exhibited the maximum yield strength of 245 MPa and ultimate tensile strength of 390 MPa. The significant improvements observed in age hardening response and tensile strength were attributed to the dense β′ plate-shape particles formed on the prismatic planes of the α-Mg matrix and cuboid-shaped Mg5(Gd,Y) particles. However, with further increase of the Gd content to 12 wt%, the size and volume fraction of the cuboid-shaped Mg5(Gd,Y) precipitates increased and these large and brittle precipitates, which may act as crack initiators, deteriorated the ductility of the alloy.