Microstructure and mechanical properties of the Mg-Gd-Y-Zn-Zr alloy fabricated by semi-continuous casting

Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy ingot with diameter of 280 mm and length of 2940 mm was successfully fabricated by semi-continuous casting. The microstructure and mechanical properties of the large ingot at different locations were investigated. The concentration of the RE and Zn elements distributed almost homogeneously through the whole alloy ingot. The average grain size decreased from the center to the surface of the alloy ingot, while the strength and ductility were improved gradually. The main eutectic compounds located at the grain boundaries were (Mg,Zn)(3)(Gd,Y) phase, adjacent to these eutectic compounds the 14H-type long period stacking ordered (LPSO) phase formed. Furthermore, some block-shaped Mg-24(Gd,Y)(5) phase and isolated Zr cores can be recognized in the interior of the grains. (C) 2012 Elsevier B.V. All rights reserved.