Microstructural evolution and mechanical performance of cast Mg-3Nd-0.2Zn-0.5Zr alloy with Y additions
(1. National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China)
2. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China)
Abstract: This work investigated the effects of different Y additions (0, 1.5, 3.0 and 4.5 wt.%) on the microstructural evolution and mechanical performance of cast Mg-3Nd-0.2Zn-0.5Zr alloy. The results show that as the Y content increases, the key secondary phases in as-cast alloys change from the Mg12Nd type to the Mg24Y5 type. Meanwhile, the number density of Zn-Zr particles in the grains of as-quenched alloys gradually decreases. HAADF-STEM observations of peak-aged samples reveal that element Y is greatly enriched in the globular β? precipitates, leading to a significantly increased volume fraction and promoted precipitation kinetics of β? precipitates, resulting in enhanced strength of the alloy. Tensile tests reveal that, with the addition of 4.5 wt.% Y, the yield strength of the base alloy is substantially increased by 88 and 61 MPa after being aged at 200 and 225 °C under peak-aged conditions, respectively.
Key words: Mg-3Nd-0.2Zn-0.5Zr alloy; Y alloying; age-hardening response; microstructural evolution; mechanical properties