Alloy Constitution and Phase Equilibria in the HfRuRh System.
I. Solidus Sur-face of the Hf–HfRu–HfRh Partial System

Abstract

The data obtained by physicochemical analysis techniques are used for the first time to determine the nature of phase equilibria in the Hf–Ru–Rh system at 50−100 at.% Hf (Hf–HfRu–HfRh partial system) at subsolidus temperatures and to construct the solidus surface on the composition triangle. It is established that there is a continuous series of solid solutions between isostructural (CsCl type) HfRu-based and high-temperature -HfRh phases. This allowed triangulation of the Hf–Ru–Rh system into two partial ones at 50 at.% Hf. The β-Hf solid solution, γ-Hf₂Rh phase (Ti₂Ni structural phase), and δ-phase, forming three single-phase regions on the solidus surface, participate in the phase equilibria at subsolidus temperatures. The ruled surfaces formed by the δ<β-Hf> and δγ tie lines fall from the bounding binary systems to the δ<β-Hf>γ isothermal plane at 1373 °С and the γ<β-Hf> ruled surface falls in turn to the Hf–Rh binary system.