Atomistic simulation of point defects and diffusion in B2 NiAl

Journal Article · Tue Aug 04 04:00:00 EDT 1998 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00206-1· OSTI ID:651159

Mishin, Y; Farkas, D ^[1]

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1. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

NiAl is a strongly ordered compound with a large atomic size difference between the components. Due to these features it demonstrates the so-called triple-defect mechanism of compositional disorder with Ni anti-structural atoms in Ni-rich compositions and Ni vacancies in Al-rich compositions. Diffusion mechanisms in triple-defect compounds are more involved than in antisite disorder compounds. Because every Ni atom in the B2 structure is surrounded by Al atoms and vise versa, every nearest-neighbor (NN) jump of a vacancy induces local disorder, which is very unfavorable. The authors therefore have to consider diffusion of Ni and Al along their own sublattices by next-nearest-neighbor (NNN) vacancy jumps. Alternatively, one can think of cycled mechanisms in which the crystal order is destroyed only locally and temporarily, but is totally restored when the diffusion cycle is complete. In this study the authors apply molecular statics simulations to evaluate the energetics of the point defect formation and migration in NiAl by different mechanisms. The goal of their simulations is to predict the mechanisms that are the easiest, thus dominating, at different alloy compositions.

• OSTI ID: 651159
• Report Number(s): CONF-980202--
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 4-5 Vol. 39; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ATOM TRANSPORT
CONCENTRATION RATIO
DIFFUSION
INTERMETALLIC COMPOUNDS
NICKEL ALLOYS
POINT DEFECTS
SIMULATION