Effects of Solution Temperature and Nd Addition on Microstructure and Mechanical Properties of Mg-12Gd-2Zn-xNd-0.4Zr Alloys

To reveal the influences of solution temperature and Nd addition on microstructures and mechanical properties of Mg-12Gd-2Zn-xNd-0.4Zr (x = 0, 0.5, and 1 wt.%) alloys, optical microscope, scanning electron microscope, tensile testing machine, nano-indentation tester, and Vickers hardness tester were used to study the microstructures and mechanical properties of the solution-treated alloys. The results show that with the increase in solution temperature, the alternating alpha-Mg and beta-(Mg, Zn)(3)Gd eutectic phase and the stacking faults (SFs) and long-period stacking ordered (LPSO) structures gradually decrease and disappear, accompanied by the increased needle-like precipitated phase. The beta-(Mg, Zn)(3)Gd and needle-like precipitated phases increase with increasing Nd addition under the same solution temperature. The yield strength and elongation are both enhanced with increasing solution temperature, the yield strength is also improved but the elongation is reduced with increasing Nd addition. Most importantly, the comprehensive mechanical property, called product of strength and elongation, is significantly improved by increasing solution temperature for the three alloys, but overall, it is reduced with increasing Nd addition solution treated at the same temperature. The Mg-12Gd-2Zn-0.5Nd-0.4Zr solution treated at 515 degrees C shows the highest product of strength and elongation (4498.4 MPa%) with the ultimate tensile strength of 335.7 MPa and elongation of 13.4%.