Molecular dynamics simulation of a swift ion track in NiAl

The phase transformations in a stoichiometric and non-stoichiometric NiAl alloy under irradiation are theoretically investigated by molecular dynamics (MD) simulation technique with many-body interatomic potentials. The kinetics of the transition of an initially B2 or bcc lattice structure is modelled under thermal conditions and under the influence of a thermal heat spike originating from the slowing down of a swift ion. The results are discussed with respect to lattice changes by projection of the lattice position and with respect to the order-disorder changes by means of a radial distribution function. It is shown that the spike induced a liquid-like structure. For the non-stoichiometric Ni62Al38 alloy the B2-L1(0) martensitic transition could be verified. The equilibrium (martensitic L1(0)) phase cannot be reached in ion tracks on the first stage, when diffusion in a solid does not play a role. Sine-like lattice oscillations are transformed into a sequence of kink-like excitations - "soliton lattice". The character of formed domain structure and the kinetics of the transition depends on the presence of a track. (C) 2004 Elsevier B.V. All rights reserved.