Lattice stability of some Ni-Ti alloy phases versus their chemical composition and disordering

A realistic n-body Ni-Ti potential is derived and applied in molecular dynamics simulation for studying the lattice stability of the terminal solid solutions and an intermetallic compound of B2 NiTi phase. It is found that when the solute contents are increased beyond two respective critical values of 15 at% of Ni and 38 at% of Ti, the crystalline lattices of the solid solutions become unstable and transform into amorphous states, suggesting that a glass-forming range of the system is from 15 to 62 at% of Ni. In the case of B2 NiTi compound, a crystalline-to-amorphous transition can result from the introduction of either a certain amount of chemical disordering or a compositional shift from its exact stoichiometry. In addition to the B2 NiTi phase, the simulation results also give some insight concerning the phase transition behaviour upon irradiation for the Ni3Ti and NiTi2 intermetallic compounds.