In-situ synchrotron X-ray diffraction investigation on deformation behavior of Nb/NiTi composite during pre-straining process
(1. School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China;
2. Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea;
3. Youke Publishing Co., Ltd., Grinm Group Co., Ltd., Beijing 100088, China;
4. School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116, China;
5. School of Materials Science and Engineering, Beihang University, Beijing 100191, China)
2. Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea;
3. Youke Publishing Co., Ltd., Grinm Group Co., Ltd., Beijing 100088, China;
4. School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116, China;
5. School of Materials Science and Engineering, Beihang University, Beijing 100191, China)
Abstract: The mechanisms responsible for deformation behavior in Nb/NiTi composite during pre-straining were investigated systematically using in-situ synchrotron X-ray diffraction, transmission electron microscopy and tensile test. It is shown that upon loading, the composite experiences elastic elongation and slight plastic deformation of B19′, B2 and β-Nb phases, together with the forward stress-induced martensitic (SIM) transformation from B2 to B19′. Upon unloading, the deformation mechanisms of the composite mainly involve elastic recovery of B19′, B2 and β-Nb phases, compression deformation of β-Nb phase and incomplete B19′→B2 reverse SIM transformation. In the tensile loading-unloading procedure, besides the inherent elastic deformation and SIM transformation, the (001) compound twins in B19′ martensite can also be conducive to the elastic deformation occurring in B19′-phase of the composite. Therefore, this composite can exhibit a large recoverable strain after unloading owing to the elastic deformation, and the partially reversible and consecutive SIM transformation together with the (001) compound twins.
Key words: Nb/NiTi composite; near-linear deformation behavior; large recoverable strain; martensitic transformation