Proton irradiation induced phase transformation in Ni-Mn-Ga thin films

Abstract

Abstract This paper reports the martensitic transformation of NiMnGa film induced by proton irradiation, which is of great significance for evaluating the reliability of NiMnGa film. Ni-Mn-Ga thin films are spotlighted as next-generation alternatives to currently used micro-actuators in the MEMS system for aircraft. Nonetheless, their potential applications are hindered by the stability under proton irradiation in the space. In the present manuscript, the microstructure evolutions of Ni50Mn25Ga25 thin films are investigated under various proton irradiation doses. A large number of point defects are introduced into the thin films at the irradiation dose over 1\xa0×\xa01016\xa0p/cm2 as indicated by the positron annihilation spectrum. And the type of defects remains the same after irradiation Consequently, 7\xa0M martensite is formed on the surface of austenitic Ni50Mn25Ga25 thin films driven by the internal stress filed based on the GI-XRD and TEM observations.