Phase Equilibria of the Cu-Ti-Er System at 773 K (500 °C) and Stability of the CuTi₃ Phase

The phase relationships of the Cu-Ti-Er ternary phase diagram at 773 K (500 °C) were investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and differential thermal analysis (DTA). It is confirmed in this work that the binary compounds Cu₉Er₂ and Cu₇Er₂ exist in the Cu-Er binary system at 773 K (500 °C). The stability of the CuTi₃ phase is confirmed in the Cu-Ti system. After heat treatment at 1023 K (750 °C) for 90 hours, the phase CuTi₃ is observed in the microstructure of the alloy 25Cu75Ti. The temperature of the eutectoid transformation, namely, β-Ti ↔ α-Ti + CuTi₃, is determined to be 1078 K (805 °C) in this work. The 773 K (500 °C) isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. None of the phases in this system reveals a remarkable homogeneity range at 773 K (500 °C).