Deformation behavior of a novel sandwich-like TiNb/NiTi composite with good biocompatibility and superelasticity

In this study, a novel sandwich-like TiNb/NiTi superelastic composite was designed and fabricated to achieve a combination of good biocompatibility and superelasticity. Experimental results revealed that the good biocompatibility of the TiNb/NiTi composite was attributed to the outer non-cytotoxic TiNb layer insulating the direct contact between the inner NiTi layer and cells, and the excellent superelasticity of the composite was mainly ascribed to two different kinds of fully reversible stress-induced martensitic (SIM) transformations, involving B2↔B19′ and β↔α″ transformations. Based on the in situ high-energy synchrotron X-ray diffraction (SXRD) technique, the deformation mechanism of TiNb/NiTi composite, involving the elastic elongation and recovery of B2, β, B19′, and α″ phases, reversible B2↔B19′ and β↔α″ SIM transformations, was clearly clarified. These results could shed some light on the design and development of novel superelastic composites for biomedical applications.