R-Phase Transformation Evolution in NiTi SMA Wires Studied via the Internal Friction Technique
Yuhao Xu,
Junlan Chen,
Xinggang Wang,
Meng Sun,
Xianping Wang,
Weibin Jiang
Affiliations
Yuhao Xu
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
Junlan Chen
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
Xinggang Wang
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
Meng Sun
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
Xianping Wang
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
Weibin Jiang
Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, as aging time increased at 450 °C, the dynamic phase transition splitting from B2 → R to B2 → R1 and B2 → R2 became evident. However, such a splitting process was not observed for the sample after aging at 400 °C. The reason for R-phase generation is attributed to non-uniformly distributed stress fields. The splitting of the internal friction peak, in conjunction with high-resolution transmission electron microscope and mechanic results, suggests a substantial occurrence of short-range segregation of Ni atoms in the B2-NiTi matrix. Furthermore, the specific damping capacity (SDC) exhibits a gradual increase with prolonged annealing time. Specifically, the sample with significant dynamic phase transition splitting reaches an SDC value of 0.60.
