Effects of trace Ca addition on microstructure and mechanical properties of as-cast Mg-Sm-Gd-based alloy
Kai Guan, Jing-huai ZHANG, Qiang Yang, Bai-shun LI, Ruizhi Wu, Jian Meng
Abstract
The effects of trace amounts of Ca on the microstructure and mechanical properties of as-cast Mg−Sm− Gd−Zn−Zr alloy were systematically investigated mainly by means of transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and tensile test. The results reveal that the dominant intermetallic compound in Mg−Sm−Gd−Zn−Zr alloy is Mg3RE phase with significant enrichment of Zn. The addition of Ca in Mg−Sm−Gd−Zn−Zr alloy can not only refine grains, but also promote the formation of Mg5RE phase and solute-enriched stacking faults (SESFs). The coherent interface indicates that Mg3RE phase can act as the nucleation site of Mg5RE phase. Finally, the decreased grain size and the formation of Mg5RE phase and SESFs in the Ca-modified alloy are beneficial to the enhancement of mechanical properties.