Alloy Constitution and Phase Equilibria in the Hf–Ru–Rh
System. IІІ. Solidus Surface of the Partial Ru–HfRu–HfRh–Rh System

Abstract

The data obtained by metallography, X-ray diffraction, and electron microprobe and differential thermal analyses, as well as incipient melting points measured with the Pirani-Alterthum method, are used to construct, for the first time, the solidus surface of the Hf–Ru–Rh system at 0−50 at.% Hf on the composition triangle. Ruthenium and rhodium solid solutions, ε and θ phases based on HfRh₃ (AuCu₃-type structure) and Hf₃Rh₅ (Ge₃Rh₅ type), and a continuous series of solid solutions between isostructural (CsCl-type) phases based on the HfRu compound and its high-temperature modification (δ phase) take place in phase equilibria. Five single-phase surfaces corresponding to solid solutions based on components and binary phases, seven ruled surfaces bounding the two-phase volumes, and three isothermal planes formed by the mentioned phases in invariant four-phase equilibria with participation of liquid (at 1900, 1810, and 1720 °С) are constituents of the solidus surface.