Experimental investigation on phase equilibria in Mg-Y-Ag system at 400 and 500?C

Phase relations of the Mg-Y-Ag ternary system in the Y < 50 at% region at 400 degrees C and 500 degrees C were ex-perimentally investigated by utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Nineteen and twelve three-phase equilibria were determined at 400 degrees C and 500 degrees C, respectively. Four new ternary compounds, i.e., tau 1, tau 2, tau 3 and tau 4, were detected in this system, and the tau 1 phase, showing a narrow composition range of Mg83.1-85.0Ag8.4-11.5Y4.9-7.2, was further refined to belong to the Fd3m space group of the diamond structure. By the way, tau 1melts congruently at 460.7 degrees C. At 500 degrees C, tau 1, tau 2, tau 3 and tau 4 phases cannot exist stably. Furthermore, with temperature increasing from 400 degrees C to 500 degrees C, the maximum solubility of Ag in Mg24Y5 decreases from 9.37 at% to 4.53 at%. The solubility of Ag in Mg2Y and MgY can be up to 12.84 at% and 7.52 at% at 500 degrees C, respectively. The present results may be of significant importance in developing new Mg-based alloys. (c) 2023 Elsevier B.V. All rights reserved.