Effect of Y for enhanced age hardening response and mechanical properties of Mg-Gd-Y-Zr alloys

In this study, compositional dependence of age hardening response and tensile properties were investigated for Mg-10Gd-xY-0.4Zr (x = 1, 3, 5 wt.%) alloys. With increasing Y content, the age hardening response of the alloys enhanced and tensile properties increased. The Mg-10Gd-5Y-0.4Zr alloy exhibited maximum tensile strength and yield strength at aged-peak hardness, and the values were 302 MPa and 289 MPa at room temperature, and 340 MPa and 267 MPa at 250 °C, respectively. The strong peak age hardening was attributed to the precipitation of prismatic β′ plates in a triangular arrangement. The cubic shaped β phase was also observed at grain boundaries. The remarkable improvement in strength is associated with a uniform and high dense distribution of β′ and cubic shaped β precipitate phases in Mg matrix. Elongation of Mg-10Gd-0.4Zr alloys decreased with increasing Y content, and the elongation of Mg-10Gd-5Y-0.4Zr alloy was less than 3% below 250 °C, whereas the alloys containing 1 wt.% and 3 wt.% Y exhibited higher elongation than 5% at room temperature.