Isothermal section of Mg-Zn-La system in Mg-rich corner at 400 ℃

Alloys with different compositions in Mg-rich corner of Mg-Zn-La system at 400 ℃ were prepared,the phase equilibrium in the Mg-rich corner of Mg-Zn-La system was determined by scanning electron microscopy(SEM),electron probe microanalysis based on energy dispersive X-ray spectroscopy(EPMA-EDS) and X-ray diffraction(XRD),and the isothermal section at 400 ℃ was established. The results show that there exists a ternary compound(T-phase) with a constant La content and changable Mg/Zn contents in the Mg-Zn-La system. The mole fraction of La in T-phase is about 8%,and that of Zn is from 16% to 43%. There exist a two-phase equilibrium which consists of T-phase plus hcp-Mg and a three-phase equilibrium which is composed of T-phase,hcp-Mg and a liquid phase(L-phase) at 400 ℃ . The L-phase consists of 70% Mg,30% Zn and is free of La.