The melting diagram of the Ti-Dy-Si system in the Ti-Ti5Si3-Dy5Si3-Dy region

The phase equilibria in the Ti-Ti5Si3-Dy5Si3-Dy part of the Ti-Dy-Si system were studied by DTA, X-ray diffraction, metallography and EPMA. The melting diagram, isopleths at 5Si, 65Ti and 65Dy, and a reaction scheme were constructed. The solidus surface is characterized by the following three-phase fields: 〈β-Ti〉 + 〈Ti5Si3〉 + 〈TiDySi〉, 〈β-Ti〉 + 〈TiDySi〉 + 〈α-Dy〉, 〈TiDySi〉 + 〈α-Dy〉 + 〈Dy5Si3〉, and 〈Ti5Si3〉 + 〈TiDySi〉 + 〈Dy5Si3〉. The first two fields form via U-type equilibria, L + 〈Ti5Si3〉 ⇄ 〈β-Ti〉 + 〈TiDySi〉 and L + 〈β-Ti〉 ⇄ 〈TiDySi〉 + 〈α-Dy〉, at 1320 and 1170 °C, respectively. The third three-phase field results from an invariant eutectic four-phase equilibrium, L ⇄ 〈TiDySi〉 + 〈α-Dy〉 + 〈Dy5Si3〉, at 1157 ± 6 °C. The fourth one is the result of a P-type equilibrium, L + 〈Ti5Si3〉 + 〈Dy5Si3〉 ⇄ 〈TiDySi〉. The temperature of the latter was estimated to be within the interval 1650-1700 °C.