Effect of Y for enhanced age hardening response and mechanical properties of Mg–Ho–Y–Zr alloys

In this study, compositional dependence of age hardening characteristics and tensile properties were investigated for Mg–4Ho–xY–0.6Zr alloys (x = 0, 3, 5, and 7 wt%). The result showed that with increasing Y content, the hardness of the alloys increased in the as-quenched and aged-peak conditions. Considerable age hardening response was recognized for the alloys. When the alloy containing 7% Y showed the most remarkable age hardening response at aging temperature of 250 °C. The tensile strength of the alloys increased monotonously with increasing Y content, and Mg–4Ho–7Y–0.6Zr exhibited the maximum ultimate tensile strength and yield strength at peak hardness, and the values were 240 and 165 MPa at room temperature, and 204 and 131 MPa at 250 °C, respectively. The improvement in strength appeared to be associated with β′ and/or equilibrium Mg24Y(Ho)5 precipitates and high dense dislocation.