In-situ synchrotron X-ray diffraction investigation on deformation behavior of Nb/NiTi composite during pre-straining process

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 beta-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 beta-Nb phases, compression deformation of beta-Nb phase and incomplete B19'& RARR;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.

Automated summary

The mechanisms responsible for deformation behavior in Nb/NiTi composite during pre-straining were systematically investigated. It was found that the composite experiences elastic elongation, slight plastic deformation, and stress-induced martensitic transformation during loading, while the deformation mechanisms during unloading mainly involve elastic recovery, compression deformation, and incomplete reverse SIM transformation.