Regensburg 2010 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.43: Poster

Tuesday, March 23, 2010, 14:45–16:30, Poster C

Simulations of the martensitic phase transition in NiTi — •Daniel Mutter and Peter Nielaba — Physics Department, University of Konstanz, 78457 Konstanz, Germany

In this work, molecular dynamics simulations of the martensitic phase transformation of NiTi are performed, which occurs between the low-temperature B19’ structure and the high temperature B2 structure. This effect is the reason for the shape memory behaviour and the extraordinary superelasticity of NiTi, which make it one of the most commonly used shape memory alloys in engineering.

In order to explore the possibility to use these effects at the nanoscale, the simulations were carried out in a range of about 1000 - 4000 particles, with a potential arising from the tight binding model in the second moment approximation ([1]).

By analyzing the deformation of the simulation box and the crystal structure during a heating-cooling process, it is shown, that the B19’ structure is stable at low temperatures and that the phase transition occurs at about 310 K for equiatomic NiTi. Further results show an extreme concentration dependence of the martensitic transition temperature, as well as the behaviour of the Gibbs free energy during the phase changes.

Because of a few not well reproduced experimental facts, first simulations with an improved potential (“modified embedded atom method” [2]) are presented.

[1] W. S. Lai, B. X. Liu, J. Phys. Cond. Mat. 12, L53-L60 (2000).

[2] Y.-M. Kim et al., Phys. Rev. B 74, 014101 (2006).