(1. 陕西理工大学 材料科学与工程学院，汉中 723001；
2. 中国石油大学（北京）新能源与材料学院，北京 102249)
摘 要: 传统NiTi形状记忆合金因其低的强度显著降低了马氏体相变的超弹稳定性，本文通过熔炼、锻造、拔丝及退火获得了平均晶粒尺寸为14 nm的NiTi和Nb纳米线复合材料，并通过循环拉伸测试研究了该复合材料马氏体相变的超弹稳定性。结果表明：用6%的应变量循环拉伸10次后，纳米晶NiTi合金/Nb纳米线复合材料呈现低的残余应变(0.52%)、高的超弹应力(748 MPa)及低的超弹应力的降低率(16%)，此综合性能优于以往研究的NiTi合金。这主要源于纳米晶NiTi合金/Nb纳米线复合材料中纳米晶粒产生的细晶强化和Nb纳米线产生的第二相强度，由此显著提高复合材料的强度并抑制马氏体相变过程中塑性变形的产生，因而提高了该复合材料马氏体相变的超弹稳定性。
关键字: 纳米晶；NiTi形状记忆合金；Nb纳米线；复合材料；超弹性
（1. School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723001, China;
2. Department of Materials Science and Engineering, China University of Petroleum Beijing, Beijing 102249, China）
Abstract:The conventional coarsed NiTi shape memory alloy often exhibits poor superelastic stability during martensitic transformation owing to their low strength. In this study, the nanocrystalline NiTi with an average grain size of 14 nm and Nb nanowires composites were obtained by melting, forging, wire drawing and annealing, the superelastic stability of composites was investigated by cyclic tensile tests. The results show that the nanocrystalline NiTi/Nb nanowire composite exhibits lower residual strain (0.52%), higher superelastic stress (748 MPa) and lower reduction rate of superelastic stress (16%) after ten cycles of loading (up to 6%)-unloading, which overall performance is improved compared to previous NiTi-based shape memory alloy. It is suggested that the improved superelastic stability of nanocrystalline NiTi/Nb nanowire composite mainly stems from enhancing the strength of the NiTi matrix by nano-grians and Nb nanowire, which resisting plastic deformation during the repetitive martensitic transformation and improving the superelastic stability.
Key words: nanocrystalline; NiTi shape memory alloy; Nb nanowires; composite; superelasticity
