Site-specifically controlling phase transformation path in Ni2MnGa shape memory alloy through ion irradiation

Reversible diffusionless martensitic transformation is the physical basis for the excellent properties of shape memory alloys. Precise control of transition behavior is generally regarded as an effective approach to improve the performance of alloys. Here, we propose a novel strategy to site-specifically control the transition behavior of Ni2MnGa shape memory alloy at the microscale. The nanoscale omega-like structure was found to appear and distribute uniformly in the parent matrix after high-energy ion beam irradiation, which resulted in the anisotropy of the {110} plane shuffling along the <110> direction. Consequently, the low-temperature phase of the sample changed from multi-variant five-layer modulated martensite to single-variant seven-layer modulated martensite. We further show that the specific phase transformation in Ni2MnGa shape memory alloys can be precisely controlled by the high-energy ion beam irradiation. This work should not only point out the potential risk of performance for the shape memory alloys serving in irradiation environments, but also contribute a novel way to fabricate more intelligent and specific-functional micro-/nano-devices of shape memory alloys.