Experimental investigation of the Mg[sbnd]Zn[sbnd]Zr ternary system at 450 °C

Abstract

The MgZnZr ternary system was experimentally investigated at 450 °C using six diffusion couples and 16 key alloys. Four new ternary compounds, IM1, IM2, IM3 and IM4 were detected. The compositions, homogeneity ranges, phase relationships and the X-ray diffraction patterns of these compounds were identified using scanning electron microscopy coupled with energy-dispersive x-ray spectrometer and x-ray diffraction techniques. The homogeneity ranges of IM1, IM2, IM3 and IM4 are Mg(23–26)Zn66Zr(8–11), Mg(15–16)Zn66Zr(18–19), Mg(10–11)Zn66Zr(23–24), and Mg(9–13)Zn(79–87)Zr(5–8), respectively. IM1 compound crystallizes in an MgZn2 structure type with hexagonal structure and P63/mmc space group. The MgZn and ZnZr binary compounds do not have extended solid solubility into the ternary system. The phase boundaries of MgZnZr liquid phase at 450 °C were determined by several key alloys. The single phase liquid region extended into the ternary phase diagram only to around 1 at.% Zr. However, phase regions containing liquid along with other phases existed in the vicinity of the MgZn side up to 10 at% Zr. Based on the current experimental results, the isothermal section of the MgZnZr ternary system at 450 °C was constructed.