Effect of Nd on the Microstructure and Mechanical Properties of Mg-La-Ce Alloys at Ambient and Elevated Temperatures
Lingyun Feng, Xixi Dong, Qing Cai, Bin Wang, Shouxun Ji
Abstract
Abstract The microstructures and tensile properties were investigated for high-pressure die-cast Mg1.6La1.0Ce alloy with different Nd contents from 0 to 3 wt.%. The results showed that fine dendritic and segmented dendritic microstructures were observed in the as-cast alloys, but the eutectic morphology changed from lamellar for low Nd-containing alloys to continuous fibrous with dendritic α-Mg in eutectics for high Nd-containing alloys. The compositions of the eutectic phase were also transferred from Mg 12 (La, Ce) in the alloys without Nd to Mg 12 (La, Ce, Nd) in the alloys with Nd addition. When the concentration of Nd was greater than 2 wt.%, numerous nanoscale Mg-Nd intermetallic phases precipitated at the grain boundaries and eutectic area. The addition of Nd was also found to increase tensile strength significantly at ambient temperature and elevated temperatures. For the alloy without Nd, the yield strength and ultimate tensile strength (UTS) was 135.6 MPa and 189.9 MPa at ambient temperature and 56.3 MPa and 57.4 MPa at 300 °C, respectively. When adding 3 wt.% Nd, the yield strength increased to 161.9 MPa at ambient temperature and 75.4 MPa at 300 °C. The UTS increased to 181.9 MPa at ambient temperature and 90.4 MPa at 300 °C. The significant improvement in strength was attributed to the strengthening from the refined structure and the dispersion of second-phases of intermetallic compounds.