Effects of proton irradiation on the microstructure and shape recovery characteristics of a NiTi alloy

Herein, we investigate the effects of proton irradiation on the structure and shape recovery characteristics of a NiTi alloy and provide a mechanistic explanation of the observed phenomena. Detailed analysis revealed that bombardment with 3 MeV protons induced the formation of a complex multilayer structure comprising TiH2, Ti2Ni, austenite and austenite-martensite layers along the irradiation direction with increasing distance and the origin of the above structure was shown to be closely related to the preferential sputtering effect and irradiation induced segregation. Finally, the shape recovery characteristics significantly deteriorated with increasing irradiation fluence, since the multilayer structure hindered the martensitic transformation.