Uniaxial tensile deformation behavior of a sandwich‐like structural TiNb‐NiTi composite for biomedical applications

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The uniaxial tensile deformation behavior of a sandwich‐like structural TiNb‐NiTi composite was investigated by uniaxial tensile test and in situ high‐energy synchrotron X‐ray diffraction (SXRD). It is found that below 1.2% macroscopic strains, the elastic deformations of the B2, β, B19′ and α″ phases take place in the TiNb‐NiTi composite. During the subsequent loading, the β → α″ and B2 → B19′ stress‐induced martensitic transformations (SIMTs) occur within the macroscopic strains of 0.5%–4.2% and the macroscopic strains of 0.7%–6.2%, respectively. At the macroscopic strain of about 4.2%, the outer TiNb layer of the TiNb‐NiTi composite experiences a partial fracture, as proved by the disappearance of (040) α″ and a sudden jump in the (110) B19′ d ‐spacing caused by load transfer. With further uniaxial tensile deformation, the TiNb‐NiTi composite finally fractures at a strain of ~ 6.2%. Our results might provide some valuable information for understanding the deformation behavior of novel sandwich‐like structural shape memory composites in more depth.