Effects of Gd and Zr additions on the microstructures and high-temperature mechanical behavior of Mg–Gd–Y–Zr magnesium alloys in the product form of a large structural casting

The microstructures, high-temperature mechanical properties, and fracture behavior of Mg–Gd–Y–Zr alloy components produced by low-pressure sand casting with different Gd and Zr contents, have been investigated. The ultimate tensile strength (UTS), tensile yield strength, and total elongation (EL) were measured within the 25–300 °C range. At the same temperatures, the UTS and yield strength (YS) of the T6 treated Mg–xGd–3Y–0.5Zr alloys increased with Gd content increasing from 9 to 11%, which was attributed to the improvement of precipitation strengthening. Increasing the Zr content from 0.3 to 0.5% leads to dramatic decrease in grain size and improved tensile properties of T6 treated Mg–10Gd–3Y–yZr alloys which is considered to be due to grain-boundary strengthening. With the increase of tensile temperature, both UTS and YS of the T6 treated Mg–xGd–3Y–yZr alloys initially increase and then decrease. The β′ precipitates provide important strengthening sources in experimental alloys, especially at elevated temperatures. The Mg–10Gd–3Y–0.5Zr alloy shows good combination of strength and EL within the 25–300 °C range.