Atomistic modeling of the site occupancies of Ti and Cu in NiAl

Abstract

In a recent paper by Wilson and Howe, experimental evidence, regarding the site occupancy of two simultaneous alloying additions to NiAl, points to the possibility of a change in site occupancy behavior with concentration. They analyzed five B2 structured NiAl-Ti-Cu alloys to determine, via Atom Location by Channeling Enhanced Microanalysis (ALCHEMI), the site occupancies of Ti and Cu in Al-deficient and stoichiometric NiAl alloys. Three alloys were produced with Cu replacing Al (Ni{sub 50}Al{sub (47{minus}x)}Ti{sub 3}u{sub X} with X = 1, 3, 6) and two were made with Cu added in place of Ni (Ni{sub (50{minus}x)}Al{sub 47}Ti{sub 3}Cu{sub X}, with X - 1, 3). Their results showed that for Al-deficient alloys both Ti and Cu show a strong preference for Al sites (over 80% for both types of atoms) while much lower Cu concentrations are found in Al sites for Ni-deficient alloys. From this limited set of experimental results, interesting conclusions were drawn suggesting a close relationship between the site preference of the alloying additions and the Ni:Al ratio. The purpose of this paper is to show that even a limited amount of experimental data, coupled with economical atomistic simulations, can constitute a powerful tool for examining specific details onmore » otherwise complex systems for which an exhaustive experimental analysis is prohibitive.« less