Constitution of Nickel-Rich Quaternary Alloys of the Ni-Cr-Ti-Al System

Abstract

The quaternary system Ni-Cr-Ti-Al has been studied up to a temperature of 1150°C for compositions greater than 50 atomic pct Ni. It has been shown that the region contains six single phase areas, namely, the face-centered-cubic nickel-rich primary solid solution γ, the face-centered-cubic orderd phase γ′ based on Ni₃Al, the hexagonal-close-packed intermetallic compound η-Ni₃Ti, and the three body-centered-cubic phases α₁-NiAl, β₂-NiTi, and β₃-Ni₂TiAl. As the temperature is raised, the volume of the quaternary tetrahedron occupied by the γ phase increases quite considerably, while that of γ′ decreases. The tie-lines across γ+γ′, γ + η, and γ′ + η two-phase fields lie almost exactly in the plane Ni₃Cr-Ni₃Al-Ni₃Ti, these three positions effectively outlining a pseudo-ternary system with the γ + γ′ + η triangle corresponding closely to a tie-plane. There is strong evidence that a four-phase field links the binary phases γ, γ′, and η with the ternary phase β₃-Ni₂TiAl.