A Sandwich-Structured Nb/Niti Composite With Good Bio-Compatibility, Near-Linear-Elastic Deformation And Large Elastic Admissible Strain

A combination of good bio-compatibility and large near-linear-elastic deformability was achieved in a novel sandwich-structured Nb/NiTi composite. This Nb/NiTi composite comprises of exterior (3-phase Nb layers and interior NiTi layer containing the (001) compound twined B19'-martensite and trace amount of B2-parent phase. The exterior nontoxic Nb layers offer the good bio-compatibility for Nb/NiTi composite by isolating the surface of the interior NiTi layer from cells. In situ synchrotron X-ray diffraction measurement reveals that besides the intrinsic elastic deformation, a slight and recoverable B2 <-> B19' stress-induced martensitic (SIM) transformation occurs in a continuous mode, which produces the extra phase transformation strain and thus contributes to the large elastic admissible strain of the Nb/NiTi composite. The large near-linear-elastic deformability in the Nb/NiTi composite is mainly due to the intrinsic elasticity, the recoverable SIM transformation proceeding in a continuous mode as well as the (001) compound twins within B19' martensite. These results may contribute to design and develop novel biomedical composites that have good bio-compatibility and large near-linear-elastic deformability.