Eur. Phys. J. B 84, 109-113 (2011)
https://doi.org/10.1140/epjb/e2011-20661-4

Regular Article

Simulation of the thermally induced austenitic phase transition in NiTi nanoparticles

Simulation of phase transitions in NiTi nanoparticles

Department of Physics, University of Konstanz, 78457 Konstanz, Germany

^a e-mail: daniel.mutter@uni-konstanz.de

Received: 12 August 2011
Received in final form: 10 October 2011
Published online: 31 October 2011

Abstract

The reverse martensitic (“austenitic”) transformation upon heating of equiatomic nickel-titanium nanoparticles with diameters between 4 and 17 nm is analyzed by means of molecular-dynamics simulations with a semi-empirical model potential. After constructing an appropriate order parameter to distinguish locally between the monoclinic B19′ at low and the cubic B2 structure at high temperatures, the process of the phase transition is visualized. This shows a heterogeneous nucleation of austenite at the surface of the particles, which propagates to the interior by plane sliding, explaining a difference in austenite start and end temperatures. Their absolute values and dependence on particle diameter are obtained and related to calculations of the surface induced size dependence of the difference in free energy between austenite and martensite.