Investigation on the micro-mechanism of martensitic transformation in nano-polycrystalline NiTi shape memory alloys using molecular dynamics simulations

In this study, the temperature- and stress-induced martensitic transformations in nano-polycrystalline nickel-titanium shape memory alloys were investigated using molecular dynamics simulations, and in turn the micro-mechanism was examined at the atomic scale. The transformation temperature and the stress hysteresis were found to decrease with the decreasing grain size when the grain size was less than 50 nm. The observed martensite variants' nucleation and growth phenomena during the martensitic transformation and its reverse one clearly demonstrated that the martensitic transformation was attributed to the formation of compound nanotwins structure inside the nano grains, which was a reasonable agreement with available experimental data. (C) 2019 Elsevier B.V. All rights reserved.