Constitution of Alloys and Phase Diagram of the Hf-Ru-Rh System.
IV. Liquidus Surface and Melting Diagram of the Partial Ru–HfRu–HfRh–Rh System

Abstract

Based on the data obtained during study of the as-cast Hf–Ru–Rh alloys in the range of compositions 0−50 at. % Hf and in accordance with the solidus surface constitution, physicochemical analysis techniques are used to construct for the first time the liquidus surface of the Ru−HfRu−HfRh−Rh partial system onto the composition triangle, the melting diagram and the reaction scheme reflecting the processes during alloy crystallization. It is shown that five surfaces of primary crystallization of a continuous series of solid solutions between isostructural (CsCl-type) phases based on the HfRu compound and its high-temperature modification (δ phase), solid solutions based on ruthenium and rhodium, as well as the ε phase based on HfRh₃ compound (AuCu₃-type structure) and the θ phase on the basis of Hf₃Rh₅ compound (Hf₃Rh₅-type structure) are parts of the liquidus surface. Three invariant four-phase processes involving liquid proceed at 1900, 1810, and 1720 °С.