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

摘要

According to the constitution of the solidus surface in the Hf-Ru-Rh system over the composition range 50-100 at.% Hf and the data obtained in studying the as-cast alloys by physicochemical analysis techniques, we constructed, for the first time, the liquidus surface of the partial Hf-HfRu-HfRh system on the composition triangle and its melting diagram. The vertical sections at 5 at.% Ru, 10 at.% Rh, and 75 and 80 at.% Hf at the ratio Ru : Rh = 1 : 1 are presented. The processes that occur when the alloys are crystallized are shown in the reaction scheme. The primary crystallization regions for a continuous series of solid solutions between isostructural (CsCl type) phases formed by the HfRu compound and its high-temperature modification (delta phase) as well as beta-Hf and gamma-Hf2Rh (Ti2Ni type) solid solutions are parts of the liquidus surface. An invariant four-phase equilibrium involving liquid, L-U + delta a double dagger dagger gamma + , is observed at 1373A degrees C in the system.