In Situ High-Energy X-Ray Diffraction Study of Load Partitioning in Nb/NiTi Nanocomposite Plate

A nanocomposite composed of Nb nanosheets and NiTi shape memory alloy was fabricated by multiple cold rolling. High-energy X-ray diffraction measurements were performed to probe the deformation behavior of each component during uniaxial tensile loading at different temperatures. It is demonstrated that, as the samples were tested at 203 K (−70 °C) and 298 K (25 °C), the NiTi matrix exhibited a martensite reorientation and a stress-induced phase transformation, respectively, while the Nb nanosheets showed a higher elastic strain (~2.5 pct) in comparison to that (~0.9 pct) of a sample tested at a higher temperature of 453 K (180 °C). The Nb nanosheets, with a volume fraction of only 13 pct, undertake an applied stress of ~90 pct as the NiTi matrix undergoes the martensitic transformation. It appears that the strengthening of Nb nanosheets is optimized as the matrix deforms by a stress-induced phase transformation or by a martensite reorientation in nanocomposite.