Phase Equilibria in the Ti-Ti5Si3-Dy5Si3-Dy Region of the Ti-Dy-Si System

摘要

Differential thermal analysis, X-ray diffraction, and metallography are employed to examine the phase equilibria in the Ti-Ti5Si3-Dy5Si3-Dy region of the Ti-Dy-Si system. Isothermal sections at 1100 and 900A degrees C, vertical sections at 5Si, 65Ti, and 65Dy isopleths, and a reaction scheme are constructed. The ternary compound TiDySi (tau) exists at experimental temperatures and has no appreciable homogeneity range. The isothermal sections at 1100 and 900A degrees C are similar and characterized by five three-phase regions (beta + (alpha-Dy) + tau, beta + (Ti3Si) + tau, (Ti3Si) + tau + (Ti5Si3), (alpha-Dy) + tau + (Dy5Si3), and (Ti5Si3) + tau + (Dy5Si3)) and respective two-phase fields. Three invariant four-phase equilibria are found in solid state: beta + (Ti5Si3) a double dagger" (Ti3Si) + tau (U-3), beta + tau + (Ti3Si) a double dagger" alpha (P-2), and beta + tau + (alpha-Dy) a double dagger" alpha (P-3) at similar to 1150, 900, and 885A degrees C, respectively. There is also a threephase equilibrium, beta + tau a double dagger" alpha, at 845A degrees C (p(4)). The phase equilibria are summarized in the reaction scheme.