Experimental determination of nickel-rich corner of Ni–Al–Ta phase diagram

Abstract

Liquid–solid and solid–state phase equilibria have been studied in the Ni–NiAl–Ni₃Ta triangle of the Ni–AI–Ta system, using a combination of several experimental techniques. Five primary phases occur in this region, including the ternary compound, π, Ni₆TaAI, which enters into equilibrium with each of the other four. Another compound, Ni₈Ta, forms in the solid state by decomposition of Ta–rich Ni solid–solutions and occurs in equilibrium with the γ, π, and δ (Ni₃ Ta) phases. The extent of these different phase fields has been determined at 1250°C and particular attention has been paid to the γ-γ′ solvus surface which has been shown to be accurately described by a second–order polynomial function of the atomic concentrations.

MST/321