کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1600760 1005175 2011 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Molecular dynamics simulation of diffusion in a (110) B2-NiAl film
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد فلزات و آلیاژها
پیش نمایش صفحه اول مقاله
Molecular dynamics simulation of diffusion in a (110) B2-NiAl film
چکیده انگلیسی

We report on the first direct molecular dynamics study of diffusion in B2-NiAl using one of the most reliable embedded-atom method potentials for this phase. The simulation is performed for near the stoichiometric composition at a temperature just below the melting temperature of the model. In the molecular dynamics simulation, an equilibrium point-defect concentration is generated and maintained by using a film sample with periodic boundary conditions only in two directions and free surfaces in the third direction. Two types of point defects – Ni vacancies and Ni antisites – are found in the bulk of the model. It is demonstrated that isolated Ni vacancies strongly dominate in concentration over all of their bound complexes with Ni antisites. Although we predict that some attractive interactions should occur between point defects to form bound Ni vacancy-Ni antisite pairs and bound Ni antisite-Ni vacancy-Ni antisite complexes, only about 2% of Ni vacancies and 1% of Ni antisites statistically randomly associate to form bound Ni vacancy-Ni antisite-Ni vacancy complexes (the so-called bound triple-defect complex). As a result, it is deduced that the triple-defect diffusion mechanism is not likely to be the dominant diffusion mechanism in the bulk of the model because this diffusion mechanism effectively requires that the Ni vacancies and Ni antisites must form bound triple-defect complexes. Furthermore, it is found that Ni atoms diffuse in the bulk of the model on average about 2.5 times faster than Al atoms. Therefore, we suggest that isolated Ni vacancies are likely to play a key role in atomic diffusion of both Ni and Al near the stoichiometric composition of B2-NiAl and, consequently, the most plausible and widely accepted candidate for dominant diffusion mechanism in B2-NiAl can be considered to be six-jump cycles of a Ni vacancy. Furthermore, we can suppose that additional next-nearest-neighbor jumps of a Ni vacancy may cause that Ni atoms diffuse faster than Al atoms.

Figure optionsDownload as PowerPoint slideHighlights
► Direct molecular dynamics study of diffusion in B2-NiAl phase near the stoichiometry.
► Equilibrium point-defect concentration is generated and maintained by using a film sample.
► Mutual Ni vacancy and Ni antisite distribution is analyzed.
► Ni and Al self-diffusion coefficients are estimated.
► Isolated Ni vacancies play the key role in atomic diffusion of both Ni and Al.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Intermetallics - Volume 19, Issue 7, July 2011, Pages 848–854
نویسندگان
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