Measurement of phase equilibria in Mg-Ag-Er ternary system

The isothermal sections of the Mg-Ag-Er ternary system at 400 °C and 500 °C have been experimentally determined by using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). 19 and 13 three-phase regions were established at 400 and 500 °C, respectively. 3 new ternary compounds, τ1, τ2, and τ3, were detected at 400 °C, all of which transformed to liquid phase at 500 °C. Especially, the phase τ1 was found to be of a face-centred cubic structure belonging to the space groupFd3¯m, with a lattice parameter of a = 16.053 Å. In addition, τ1 melts at about 439.1 °C and the composition range of τ1 is Mg81.89–84.38Ag9.20–11.33Er5.39–7.69. The present study can provide substantial experiments for thermodynamic optimization of the Mg-Ag-Er system, and helpful for Mg-based alloy design. •Isothermal sections of the Mg-Ag-Er system at 400 and 500 °C were constructed.•Three stable ternary phases, τ1, τ2 and τ3, were newly discovered.•Crystal structure of τ1 was revealed.