Effects of porosity and cyclic deformation on phase transformation of porous nanocrystalline NiTi shape memory alloy: An atomistic simulation

Utilizing molecular dynamics simulation, this study aims to explore the phase transformation behavior of porous nanocrystalline (NC) NiTi shape memory alloys (SMAs) when subjected to cyclic deformation. The influences of porosity and cyclic deformation on the phase transformation of NC NiTi SMAs are examined and discussed. The simulation results show that the increase in the porosity and number of cycles leads to a decrease in both the critical phase transformation stress and peak stress whereas an increase in the residual martensite, phase boundary, and interstitial atoms; the related results can be supported by previous experiments. After cyclic deformation, the reduction in the potential energy for the entire system during the tensile phase occurs at an earlier stage, indicating that the martensitic transformation occurs earlier as the number of cycles increases. Notably, the dissipated energy demonstrates a decrease with an increasing number of cycles, and the potential energy during the austenite elastic unloading stage undergoes a transition from a decreasing to an increasing trend due to the presence of residual martensite increasing with the number of cycles.

Automated summary

This study utilizes molecular dynamics simulation to investigate the phase transformation behavior of porous nanocrystalline NiTi shape memory alloys under cyclic deformation. The results show that an increase in porosity and number of cycles leads to a decrease in critical phase transformation stress and peak stress, while increasing residual martensite, phase boundary, and interstitial atoms. Additionally, the martensitic transformation occurs earlier with an increasing number of cycles, and the dissipated energy decreases. The potential energy during the austenite elastic unloading stage transitions from a decreasing to an increasing trend due to the presence of residual martensite increasing with the number of cycles.