Phase Equilibria of the Mg-Y-Zn System at 500 °C in the Mg-Rich Region

Abstract

The Mg-rich phase equilibria of the Mg-Y-Zn system at 500 °C were investigated with equilibrated alloys, by means of electron probe microanalysis and x-ray diffraction. A partial isothermal section of < 34 at.% Y and < 50 at.% Zn was constructed and an extended section of < 50 at.% Y was produced by integrating our previous results in the Zn-rich region. Following the previous finding of seven ternary phases (τ1 to τ7) in the Zn-rich region, seven more ternary phases (τ8 to τ14) were found in the Mg-rich region in the present work. With the systematic composition measurement and XRD analysis, six of them (τ8 to τ13) were determined to be the so-called LPSO phases. They are very close to one another in composition and located approximately along the line of Y/Zn ratio = 4/3. τ8 is believed to be X-Mg12YZn (14H), τ9 to be Mg10ZnY (18R) and τ13 to be 10H.