Phase-stress partition and stress-induced martensitic transformation in NbTi/NiTi nanocomposite

The phase-stress partition and stress-induced martensitic transformation in a NbTi/NiTi nanocomposite were investigated by employing in situ synchrotron x-ray diffraction during tensile cycling. The phase-stress partition behavior in the nanocomposite is significantly different from that previously reported in the metal-matrix composites. Beyond the initial elastic deformation, the stress carried by the NbTi nanowires increased significantly with increasing macroscopic strain, while the stress taken by the NiTi matrix decreased gradually. We also found that the stress-induced martensitic transformation of the NiTi matrix still proceeded even though the matrix carried decreasing stress rather than constant or increasing stress well known in binary NiTi alloys.