Vacancies in NiTi shape memory alloys

13th International Workshop on Slow Positron Beam Techniques and Applications

Weber, M.H.^1 ; Ablekim, T.^1 ; Lynn, K.G.^1

Center for Materials Research, Washington State University, Pullman WA 99164-2711, United States^1

关键词: Annealing temperatures;    Austenitic;    NiTi shape memory alloys;    Positron beams;    S values;    Thermal vacancies;    Transition regions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/505/1/012006/pdf
DOI  :  10.1088/1742-6596/505/1/012006

来源: IOP

【 摘 要 】

NiTi shape memory alloys were examined with a mono-energetic positron beam. The thermal vacancy formation enthalpy was found to be 0.77±0.08 eV. Upon heating NiTi the martensitic S value is retained to temperatures significantly above the phase transition temperature and then decreases towards the austenitic value only gradually. In contrast upon cooling, a narrow transition region at 81.5±1.5 °C is observed. The magnitude of the transition strongly depends on the annealing temperature.