采用电弧熔炼、锻造和拔丝方法原位合成了一种高Nb含量的NiTi-NbTi记忆合金复合材料。TEM显微分析显示，在材料内部纳米尺度的NbTi和NiTi纤维沿丝材轴向交替分布，NbTi纤维体积分数高达约70%。通过同步辐射高能X射线原位拉伸实验研究了复合材料的变形机制。结果显示，虽然NiTi体积分数仅约30%，但复合材料的变形仍受NiTi的应力诱发相变控制。在加载初期，复合材料先发生均匀变形，并且在拉伸曲线出现屈服平台之前，NiTi已发生均匀相变。当平台出现之后，NiTi转而发生Lüders带型相变，进而诱发NbTi也随之发生Lüders带型变形，使整个复合材料都展现Lüders带型变形。Lüders带前沿存在载荷转移现象，载荷由正在发生相变的B2-NiTi同时转移到NbTi相及之前在均匀相变过程中形成的B19'-TiNi马氏体相。

A previous study proposed a novel Nb nanowire-reinforced NiTi shape memory alloy composite possessing high yield strength (> 1.6 GPa), low apparent Young's modulus (< 30 GPa), and large quasilinear elastic strain (> 6%). This composite occupies a unique spot on the chart of the mechanical properties of conventional bulk metals, ceramics, and polymer materials. It can be used in dental braces, cardiac pacemakers, implantable devices, and flexible medical instruments. Furthermore, this study suggested that when the NiTi shape memory alloy was adopted as a matrix, the stress-induced martensitic transformation of NiTi would help the embedded nanowire reinforcement to exhibit inherent high strength. Ultralarge elastic strain (4%-7%) of Nb nanowires has been observed in these NiTi-Nb composites. Tailoring superior structural-functional properties by combining a shape memory alloy with other nanoreinforcements have recently gained research attention in materials science research focus. However, in most previous works, the volume fractions of the embedded Nb nanowires were not > 25%. It is reasonable to assume that an increase in the volume fraction of Nb nanowire would further improve the strength of the composite, and make the mechanical performance of the bulk composite much closer to that of a single nano reinforcement. As a result, a study on the high volume fraction of an Nb nanowire-reinforced NiTi shape memory alloy composite is crucial. Herein, an in situ NiTi-NbTi shape memory alloy composite with a high Nb volume fraction was prepared through arc melting, forging, and wire drawing. The microscopic analysis showed that NbTi and NiTi nanofibers were alternatively distributed in the composite along the wire axial direction. In situ synchrotron X-ray diffraction measurements were carried out to study the deformation mechanism of the composite. Results revealed that although the volume fraction of NiTi was only about 30%, the deformation of the composite was mainly controlled by the martensitic transformation of NiTi. The prepared composite showed a homogenous deformation and homogenous martensitic phase transformation before the yielding. It then exhibited Lüders-like deformation that originated from the Lüders-like stress-induced martensitic phase transformation in the region of yielding. Stress transfer was observed in the Lüders band front from the transforming B2-NiTi phase to the NbTi phase and simutaneously to the previously existing B19'-NiTi martensite phase generated during the homogenous martensitic phase transformation process.