Role of point defects in stress-induced martensite transformations in NiTi shape memory alloys: A molecular dynamics study

Shape-memory properties of equiatomic NiTi rely on the thermal- or stress-induced reversible martensitic phase transformation between the B2 and B19' phases. Irradiation defects suppress thermal-induced transformations, but their effects on stress-induced transformations are poorly understood. We use molecular dynamics to investigate the effect of vacancies, vacancy clusters, interstitials, and antisite defects on stress-induced transformations. All defects suppress the transformation, but vacancy clusters do so to the greatest extent, while antisite defects do so to the least extent. The responsible mechanisms are grain boundary pinning and chemical disordering.

Automated summary

The effect of vacancies, interstitials, and antisite defects on stress-induced phase transformation in equiatomic NiTi alloy was investigated using molecular dynamics simulation. The results show that all defects suppress the transformation, with vacancy clusters having the greatest suppressive effect and antisite defects having the least. The responsible mechanisms are grain boundary pinning and chemical disordering.