(1. 陜西理工大學(xué) 材料科學(xué)與工程學(xué)院，漢中 723001；
2. 中國石油大學(xué)（北京）新能源與材料學(xué)院，北京 102249)
摘 要: 傳統(tǒng)NiTi形狀記憶合金因其低的強(qiáng)度顯著降低了馬氏體相變的超彈穩(wěn)定性，本文通過熔煉、鍛造、拔絲及退火獲得了平均晶粒尺寸為14 nm的NiTi和Nb納米線復(fù)合材料，并通過循環(huán)拉伸測試研究了該復(fù)合材料馬氏體相變的超彈穩(wěn)定性。結(jié)果表明：用6%的應(yīng)變量循環(huán)拉伸10次后，納米晶NiTi合金/Nb納米線復(fù)合材料呈現(xiàn)低的殘余應(yīng)變(0.52%)、高的超彈應(yīng)力(748 MPa)及低的超彈應(yīng)力的降低率(16%)，此綜合性能優(yōu)于以往研究的NiTi合金。這主要源于納米晶NiTi合金/Nb納米線復(fù)合材料中納米晶粒產(chǎn)生的細(xì)晶強(qiáng)化和Nb納米線產(chǎn)生的第二相強(qiáng)度，由此顯著提高復(fù)合材料的強(qiáng)度并抑制馬氏體相變過程中塑性變形的產(chǎn)生，因而提高了該復(fù)合材料馬氏體相變的超彈穩(wěn)定性。
關(guān)鍵字: 納米晶；NiTi形狀記憶合金；Nb納米線；復(fù)合材料；超彈性
（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
