Molecular dynamics study of phase transformations in NiTi shape memory alloy embedded with precipitates

Abstract

The present study utilizes molecular dynamics simulations to study the athermal and stress-induced martensitic transformation of B2 to B19′ phase in a Ni-Ti alloy and the effect of precipitates on the phase transformation. The simulations demonstrate the existence of an intermediate B19 phase between martensite and austenite phases. The Nickel-Titanium shape memory alloy with precipitates is studied by introducing Ni _3 Ti, NiTi _2 and Ni _4 Ti _3 precipitates individually using atomistic simulations. The results show that the phase transition temperature decreases in the presence of a large volume fraction of precipitates. A blended precipitates model with Ni _3 Ti and NiTi _2 is simulated to study the phase transformation in equiatomic NiTi alloy. The results indicate that the precipitates would initiate the emergence of the B19 phase and reduce the transition temperature. In addition, the variation of Nickel content by embedded precipitates would lead to a change in the microstructural phenomena.

Keywords

• NiTi alloy
• phase transformation
• molecular dynamics