Analysis of the β′Ni2TiAl/βNiTi equilibrium in Ni-Ti-Al alloys by the cluster variation method

Abstract

Abstract The cluster variation method with the Lennard-Jones potential, previously used to analyze the γ′(L1 2 Ni 3 Al)/γ(fcc Ni) equilibrium in Ni-Al base multicomponent alloys, was used to calculate the β′(L2 1 Ni 2 TiAl)/β (B2 NiTi) equilibrium phase boundaries in the Ni-Ti-Al system. Results are compared with the isothermal and vertical sections of the ternary phase diagram in the literature. The lattice misfit between β′ and β compound lattices, which is considered to play an important role for the formation of a rafted structure, passed through a minimum at 50%Ni, but was considerably larger compared to γ′/γ alloys. It is thus necessary to consider alloying addition for the optimization of high temperature properties of β′/β alloys by controlling the size and distribution of the β′ phase and the lattice misfit. © 1997 Elsevier Science Limited. All rights reserved