Alloy Constitution and Phase Equilibria in the Hf–Ru–Rh System.
II. Liquidus Surface, Melting Diagram, and Vertical Sections of the Hf–HfRu–HfRh Partial System

Abstract

According to the constitution of the solidus surface of the Hf–Ru–Rh system in the composition range 50−100 at. % Hf and based on the data obtained in studying the as-cast alloys by physicochemical analysis techniques, we constructed for the first time the liquidus surface projection of the Hf–HfRu–HfRh partial system onto the composition triangle and the melting diagram. The vertical sections at 5 at. % Ru, 10 at. % Rh, and 75 and 80 at. % Hf as well as at the ratio Ru : Rh = 1 : 1 are presented. The processes during alloys crystallization are shown in the reaction scheme. Surfaces of primary solidification of a continuous series of solid solutions between isostructural (CsCl-type) phases based on the HfRu compound and high-temperature modification of HfRh (δ phase), β-hafnium solid solution, and the Hf₂Rh-based γ phase (Ti₂Ni-type structure) are parts of the liquidus surface. An invariant four-phase equilibrium involving liquid, L_U + δ ⇄ γ + <β-Hf>, is observed at 1373 °С in the system.