Effects of Gd and Zr additions on the microstructures and hightemperature 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 degrees 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 beta' 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 degrees C range.