Exploration of Trade-Off Between Elastic Modulus and Strength of Mg–Gd–Y–Nd–Zr Alloy by Regulating Intermetallic Phases Through Si Addition

In this study, low-cost Si was added to an Mg–8Gd–4Y–1Nd–0.5Zr alloy to regulate the intermetallic phases. The mechanical properties of 0, 0.5, and 1.0 wt% Si-added alloys were studied to explore the trade-off between the elastic modulus and strength. The microstructures were characterized through metallographic microscopy, scanning electron microscopy applying energy dispersive spectroscopy, and transmission electron microscopy. The microstructures demonstrated that Y5Si3 and GdSi phases formed and consumed the solid soluble Gd and Y elements, thus reducing the amount of precipitation and increasing the size of the β′ phase. Correlations between the elastic modulus and the intermetallic phase indicated that the Y5Si3 and GdSi phases formed by the addition of Si were the mainly responsible for the improvement in the elastic modulus. The change in strength through the addition of Si was calculated, and the results revealed that such an addition could increase the elastic modulus but with a reduction in the alloy strength. The addition of 0.5 wt% Si alloy resulted in a relatively high comprehensive performance, with an elastic modulus of 46 GPa, a tensile strength of 278 MPa, a yield strength of 226 MPa, and an elongation of 4.9% under a cast-T6 state.