# Mean field theory of point defects in $\beta -NiAl$

Gururajan, MP and Abinandanan, TA (2000) Mean field theory of point defects in $\beta -NiAl$. In: Intermetallics, 8 (7). pp. 759-767.

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Official URL: http://dx.doi.org/10.1016/S0966-9795(00)00005-4

## Abstract

We have used a mean field theory to study the equilibrium concentrations of vacancies and antisite defects in each sublattice of $\beta -NiAl$ in the composition range between 45 and 55 at% Al and in the temperature range 800-2000 K. The interatomic potentials, which are inputs to the theory, are extracted from recently reported (continuous) pair potentials of Finnis-Sinclair type. The predominant defect in the stoichiometric alloy is a combination of an Ni-antisite defect and two vacancies on the Ni sublattice. The Alrich alloys of composition $(50+\Delta)$ at% contain $2\Delta %$ vacancies; since the alloys are almost perfectly ordered, these vacancies predominantly occupy the Ni Sublattice. Similarly, the Ni-rich alloys of composition $(50-\Delta )$ at% contain $\Delta$% Ni antisites. Both the vacancies on the Ni sublattice (in Al-rich alloys) and Ni-antisites (in Ni-rich alloys) show negligible temperature dependence, and hence owe their origin to the off-stoichiometry. In all the alloys, the Al-antisites have the lowest concentration (of the order $10^{-6}$ even at 2000 K). We have critically compared our theoretical results with available experimental ones.

Item Type: Journal Article Copyright of this article belongs to Elsevier Science. Nickel aluminides, based on NiAl;Defects:constitutional vacancies;Defects: point defects;Defects:theory Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 11 Aug 2006 22 Feb 2012 08:26 http://eprints.iisc.ernet.in/id/eprint/8014