Effects of Thermal Cycling and Porosity on Phase Transformation of Porous Nanocrystalline NiTi Shape Memory Alloy: An Atomistic Simulation

BF Liu and YY Wang and WP Wu, ADVANCED ENGINEERING MATERIALS, 25 (2023).

DOI: 10.1002/adem.202301019

Herein, the effects of thermal cycling and porosity on the martensitic phase transformation behavior of porous nanocrystalline (NC) NiTi shape memory alloys (SMAs) at the atomic scale are investigated by molecular dynamics simulation. The simulation results show that thermal cycling causes the NC NiTi SMAs to repeatedly undergo martensitic phase transformation and inverse phase transformation processes. The martensitic phase transformation capability is suppressed with increasing porosity and number of cycles, but the suppression effect of thermal cycling is weakened with increasing porosity. Moreover, the start temperature of martensitic transformation, residual martensitic phase, and the fraction of interstitial atoms increase with increasing porosity. Thermal cycling causes the disordered structures and shear plastic deformation to accumulate as cycling increases. Recoverable shear deformation is generated within the grain, but shear plastic deformation is mainly concentrated at both grain boundaries and pore surfaces. Residual martensitic phase increases after thermal cycling. These results provide important explanations and references for a deeper understanding of phase transformation behavior and pore effects caused by thermal cycling. Effects of thermal cycling and porosity on phase transformation of porous nanocrystalline NiTi shape memory alloys are studied using molecular dynamics simulations. The temperature-induced martensitic phase transformation behavior under thermal cycling is investigated at the atomic scale. The average atomic volume, atomic structure, phase fraction, and shear strain distribution during thermal cycling are analyzed.image & COPY; 2023 WILEY-VCH GmbH

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