Interactions between martensitic NiTi shape memory alloy and Nb nanowires in composite wire during tensile deformation

This study investigated the interactions between martensitic NiTi shape memory alloy and Nb nanowires in composite wire during tensile loading by means of in-situ high-energy X-ray diffraction. Nb nanowires have significant influence on the transformation behavior, annealed texture, and martensite variant reorientation behavior including texture evolution and load transfer among martensite variants of NiTi matrix. Meanwhile, the existence of densely distributed Nb nanowires increases the internal stress in NiTi matrix generated during martensite reorientation process, and causes the negative axial lattice stresses of all unfavored NiTi martensite variants after reorientation when the composite wire is under axial tensile stress. In addition, an exceptionally large elastic strain of 4.7% was produced over Nb nanowires after tensile deformation. Meanwhile, heterogeneous strain distribution exists in Nb nanowires, and it is associated with heterogeneous martensite reorientation strain of NiTi matrix.