Microstructure and mechanical properties of Mg–5Gd–2Y–2Zn–0·5Zr alloy

Abstract

Microstructures and mechanical properties of the Mg–5Gd–2Y–2Zn–0·5Zr alloy (wt-%) in the as cast and solution treated conditions have been investigated using optical microscopy, scanning electron microscope, X-ray diffraction, electron probe X-ray microanalyser and transmission electron microscope. The results show that after adding the element Y, the as cast Mg–5Gd–2Y–2Zn–0·5Zr alloy forms the Mg₁₂Zn(Y, Gd) phase with 18R-long period stacking ordered (LPSO) structure, and the Gd atoms in the phase can slow down the transition process of 18R to 14H in high temperature treatment. LPSO phase in the grain boundary can ensure the strength of the alloy at room and elevated temperature through effectively preventing grain boundary sliding. At 250°C, the alloy has shown the similar ultimate tensile strength and tensile yield strength under room temperature, 241 and 130 MPa respectively, and both with excellent elongation.

Keywords:

• Mg–5Gd–2Y–2Zn–0·5Zr alloy
• LPSO structure
• Microstructure
• Mechanical properties

Acknowledgements

This research was supported by the National Natural Science Foundation of China (grant no. 50875031), the National High-tech Research and Development Program of China (grant no. 2009AA03Z525) and the Aviation Science Foundation of China (grant no. 20095263005).