形状记忆合金的相变和力学性能受机械加工过程影响明显。在850 ℃下将Ti50Ni50-xAlx (x=1,2,4)形状记忆合金轧制成为板材。采用扫描电镜、透射电镜和X射线衍射对合金的微观结构研究表明:合金由NiTi相和Ti2Ni相组成,Al元素在Ti2Ni相中的固溶度比在TiNi相中高。差示扫描量热分析和电阻-温度测试表明:随着Al元素原子分数的增加,合金R相变和马氏体相变温度均下降,而两个相变之间的温度差增大。经850 ℃轧制以后,合金中Ti2Ni相减少,NiTi相中Al元素增加,从而使合金R相变和马氏体相变温度进一步降低,两个相变之间的温度差进一步增加,同时提高了合金的室温塑性。
The phase transformations and mechanical properties of shape memory alloys are remarkably affected by mechanical processing. In this study shape memory alloys Ti50Ni50-xAlx (x=1, 2, 4) are rolled into a plate at 850 ℃. The microstructures of the alloys are investigated by scanning electronic microscopy, transmission electron microscopy and X-ray diffraction. The results show that the alloys are composed of NiTi and Ti2Ni phases and the solid solubility of Al in the latter is higher than that in the former. The differential scanning calorimetry and electric resistance vs temperature measurements indicate that with the increasing Al content both the R and martensitic transformation temperatures decrease, and the temperature difference between the two transformations is enlarged. After hot-rolling at 850 ℃, the volume ratio of the Ti2Ni phase in the alloy decreases and the solid solubility of Al in the NiTi phase increases. Furthermore, the hot-rolling induces the decrease of R and martensitic transformation temperatures and the increase of their transformation temperature difference as well as the improvement of plasticity of the alloys at room temperature.
[1] 杨大智. 智能材料与智能系统[M]. 天津: 天津大学出版社, 2000: 140. Yang Dazhi. Intelligent materials and system [M]. Tianjin: Tianjin University Press, 2000: 140. (in Chinese)
[2] 郑玉峰, 赵连城. 生物医用镍钛合金[M]. 北京: 科学出版社, 2004: 174. Zheng Yufeng, Zhao Liancheng. Biomedical NiTi alloys[M]. Beijing: Science Press, 2004: 174. (in Chinese)
[3] Hwang C M, Wayman C M. Compositional dependence of transformation temperatures in ternary TiNiAl and TiNiFe alloys[J]. Scripta Metallurgica, 1983, 17(3): 381-384.
[4] Hwang C M, Wayman C M. Phase transformations in TiNiFe, TiNiAl and TiNi alloys[J]. Scripta Metallurgica, 1983, 17(11): 1345-1350.
[5] 韩冬, 刘福顺, 李岩, 等. 不同壁厚的TiNiFe 形状记忆合金管接头紧固力的模拟计算[J]. 航空学报, 2006, 27(4): 703-707. Han Dong, Liu Fushun, Li Yan, et al. Simulation calculation of the tie-in clasp stress of the TiNiFe SMA tube[J]. Acta Aeronautica et Astronautica Sinica, 2006, 27(4): 703-707. (in Chinese)
[6] Hwang C M, Wayman C M. Electron microscopy studies of martensitic transformation in ternary TiNiAl alloys [J]. Scripta Metallurgica, 1983, 17(12): 1449-1453.
[7] Hsieh S F, Wu S K. Study on the nickel-rich ternary Ti-Ni-Al shape memory alloys[J]. Journal of Materials Science, 1997, 32(4): 989-996.
[8] Edmonds K R, Hwang C M. Phase transformations in ternary TiNiX alloys[J]. Scripta Metallurgica, 1986, 20(5): 733-737.
[9] Hsieh S F, Wu S K. A study on a Ti52Ni47Al1 shape memory alloy[J]. Journal of Materials Science, 1999, 34(7): 1659-1665.
[10] Liu K T, Duh J G. Hardness evolution of NiTi and NiTiAl thin films under various annealing temperatures[J]. Surface and Coatings Technology, 2008, 202(12): 2737-2742.
[11] 刘晓山, 何国求, 陈成澍, 等. TiNiAl 合金形状记忆及超弹性效应研究[J]. 功能材料, 2006, 37(6): 912-914. Liu Xiaoshan, He Guoqiu, Chen Chengshu, et al. The research of shape memory effect and superelasticity of a TiNiAl alloy[J]. Journal of Functional Materials, 2006, 37(6): 912-914. (in Chinese)
[12] 刘晓山, 何国求, 陈成澍, 等. TiNiAl合金微观组织结构研究[J]. 同济大学学报: 自然科学版, 2007, 35(4): 515-518. Liu Xiaoshan, He Guoqiu, Chen Chengshu, et al. A study of microstructure of a TiNiAl alloy[J]. Journal of Tongji University: Natural Science, 2007, 35(4): 515-518. (in Chinese)
[13] Li Y, Liu Z M, Xiao L. Phase transformations and mechanical properties of NiTiAl shape memory alloys with equal Ni/Ti atom ratio//International Conference on Advanced Materials Development and Performance 2008. 2008.
[14] Meng L J, Li Y, Zhao X Q, et al. The mechanical properties of Ni50-xTi50Alx alloys (x=6, 7, 8, 9)[J]. Intermetallics, 2007, 15(5-6): 814-818.
[15] 李志云, 刘福顺, 徐惠彬.Fe元素对TiNi形状记忆合金相变点和力学性能的影响[J]. 航空学报, 2004, 25(1): 84-87. Li Zhiyun, Liu Fushun, Xu Huibin. Influence of Fe addition on phase transformation temperatures and mechanical properties of TiNi shape memory alloys[J]. Acta Aero- nautica et Astronautica Sinica, 2004, 25(1): 84-87. (in Chinese)
[16] Liu F S, Ding Z, Li Y, et al. Phase transformation behaviors and mechanical properties of TiNiMo shape memory alloys[J]. Intermetallics, 2005, 13(3-4): 357-360.
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