The melting diagram of the Ti–Dy–Si system in the Ti–Ti 5Si 3–Dy 5Si 3–Dy region

Abstract

The phase equilibria in the Ti–Ti 5Si 3–Dy 5Si 3–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〉 + 〈Ti 5Si 3〉 + 〈TiDySi〉, 〈β-Ti〉 + 〈TiDySi〉 + 〈α-Dy〉, 〈TiDySi〉 + 〈α-Dy〉 + 〈Dy 5Si 3〉, and 〈Ti 5Si 3〉 + 〈TiDySi〉 + 〈Dy 5Si 3〉. The first two fields form via U-type equilibria, L + 〈Ti 5Si 3〉 ⇄ 〈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〉 + 〈Dy 5Si 3〉, at 1157 ± 6 °C. The fourth one is the result of a P-type equilibrium, L + 〈Ti 5Si 3〉 + 〈Dy 5Si 3〉 ⇄ 〈TiDySi〉. The temperature of the latter was estimated to be within the interval 1650–1700 °C.