Constitution of nickel-rich quinary alloys in the system Ni-Fe-Cr-Ti-Al

Abstract

A systematic study of nickel-rich quinary alloys of the Ni-Fe-Cr-Ti-Al system has been made, confining attention to the 750° and 1000°C isothermals of the pseudo-quaternary section Ni₃Cr-Ni₃Fe-Ni₃Ti-Ni₃Al. Only three phases are involved, the nickel-rich face-centered-cubic primary γ-solid solution, the ordered face-centered-cubic Berthollide γ′-phase based on Ni₃Al, and the hexagonal-close-packed Daltonide, η-Ni₃Ti. The ternary face, Ni₃Fe-Ni₃Al-Ni₃Ti, of the pseudo-quaternary tetrahedron is very similar to the ternary face Ni₃Cr-Ni₃Al-Ni₃Ti because of iron replacing chromium atom for atom in the two face-centered-cubic phases, γ and γ′. The extent of the γ-solid solution increases considerably as the temperature is raised, while γ′ and η remain substantially unchanged. The tie-lines linking the γ and γ′-phases radiate uniformly across the γ + γ′ two-phase field of the pseudo-quaternary tetrahedron. Alloys situated near the Ni₃Fe corner of the tetrahedron are strongly ferromagnetic. The boundary separating the magnetic from the nonmagnetic γ-phase alloys at room temperature is defined by a plane lying parallel to the Ni₃Cr-Ni₃Ti-Ni₃Al face of the system and containing chromium and iron in the atomic ratio 60:40.