凝固冷却梯度对铸态NiTiNb形状记忆合金微观组织和马氏体相变的影响
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摘要
通过真空感应熔炼辅以石墨铸模冷却的方法制备了NiTiNb合金铸锭。由于石墨铸模出色的导热能力,在合金凝固过程中自下而上形成了一定的冷却梯度。采用光学显微镜(OM)以及高分辨扫描电子显微镜(SEM)等手段对铸锭不同位置的微观组织进行了表征研究,并利用X射线衍射(XRD)和差示扫描量热仪(DSC)对比分析了各位置的组成相以及马氏体相变特征。结果表明,凝固过程的冷却梯度对合金微观组织和相变行为具有明显影响。冷速较快的部位枝晶组织较为细小,而冷速较慢的部位则枝晶粗大。凝固冷却梯度虽然不会改变合金的组成相类别,但会对β-Nb相含量以及Nb元素在NiTi基体相中的固溶量造成影响,较快的冷却速度将会减少合金中的β-Nb相,同时增加Nb在NiTi相中的固溶水平。此外,冷速较快的部位其相变曲线峰型具有窄和高的特征,相变滞后也相对更宽。
The NiTiNb cast ingot was produced by vacuum induction melting combined with a graphite mold. Due to the excellent heat conductivity of graphite,cooling gradient from bottom to top of the ingot was formed. Microstructure of the cast ingot with different locations were observed using optical microscope( OM) and high resolution scanning electron microscope( SEM). The constituent phases were identified using X-ray diffraction( XRD). The martensitic transformations in cooling and heating progress were tested using differential scanning calorimetry( DSC). The results indicated that cooling gradient during solidification influenced microstructure and phase transformation of the alloy significantly. Fine dendrite structure could be obtained with rapid cooling while coarse one would be made by slow cooling during solidification process. Cooling gradient did not change the type of component phases,but would affect the content of β-Nb phase and Nb element which dissolved in Ni Ti matrix. Rapid cooling would decrease the content of β-Nb phase and increase the level of Nb in Ni Ti phase. Furthermore,a higher cooling rate also made the peak of phase transformation curve narrower and higher,and a wider hysteresis could also be obtained.
The NiTiNb cast ingot was produced by vacuum induction melting combined with a graphite mold. Due to the excellent heat conductivity of graphite,cooling gradient from bottom to top of the ingot was formed. Microstructure of the cast ingot with different locations were observed using optical microscope( OM) and high resolution scanning electron microscope( SEM). The constituent phases were identified using X-ray diffraction( XRD). The martensitic transformations in cooling and heating progress were tested using differential scanning calorimetry( DSC). The results indicated that cooling gradient during solidification influenced microstructure and phase transformation of the alloy significantly. Fine dendrite structure could be obtained with rapid cooling while coarse one would be made by slow cooling during solidification process. Cooling gradient did not change the type of component phases,but would affect the content of β-Nb phase and Nb element which dissolved in Ni Ti matrix. Rapid cooling would decrease the content of β-Nb phase and increase the level of Nb in Ni Ti phase. Furthermore,a higher cooling rate also made the peak of phase transformation curve narrower and higher,and a wider hysteresis could also be obtained.
引文
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[11] Jiang P C,Zheng Y F,Tong Y X,Chen F,Tian B,Li L,Gunderov D V,Valiev R Z. Transformation hysteresis and shape memory effect of an ultrafine-grained Ti Ni Nb shape memory alloy[J]. Intermetallics,2014,54:133.
[12] Xiao Y,Zeng P,Lei L P. Influence of peak stress on plastic behavior of Ni Ti shape memory alloy under cyclic deformation[J]. Journal of Plasticity Engineering,2017,24(1):145.(萧遥,曾攀,雷丽萍.峰值应力对Ni Ti形状记忆合金循环变形塑性行为的影响[J].塑性工程学报,2017,24(1):145.)
[13] Hamilton R F,Lanba A,Ozbulut O E,Tittmann B R.Shape memory effect in cast versus deformation-processed Ni Ti Nb alloys[J]. Shape Memory and Superelasticity,2015,1(2):117.
[14] Bewerse C,Brinson L C,Dunand D C. Microstructure and mechanical properties of as-cast quasibinary Ni Ti-Nb eutectic alloy[J]. Materials Science&Engineering A,2015,627(1):360.
[15] Zhang C S,Wang Y Q,Chai W,Zhao L C. The study of constitutional phases in a Ni47Ti44Nb9shape memory alloy[J]. Materials Chemistry and Physics, 1991,28:43.
[16] Piao M,Miyazaki S,Otsuka K,Nishida N. Effects of Nb addition on the microstructure of Ti-Ni alloys[J].Materials Transactions JIM,1992,33(4):337.
[17] Chen Y,Jiang H,Rong L,Xiao L,Zhao X. Mechanical behavior in Ni Ti Nb shape memory alloys with low Nb content[J]. Intermetallics,2011,19:217.
[18] Wang M,Jiang M,Liao G,Guo S,Zhao X. Martensitic transformation involved mechanical behaviors and wide hysteresis of Ni Ti Nb shape memory alloys[J].Progress in Natural Science:Materials International,2012,22(2):130.
[2] Yin X,Mi X,Li Y,Gao B. Microstructure and properties of deformation processed polycrystalline Ni47Ti44Nb9shape memory alloy[J]. Journal of Materials Engineering and Performance,2012,21(12):2684.
[3] Wang L,Yan D S,Jiang Z M,Rong L J. Research and development of Ni-Ti-Nb shape memory alloy pipejoint with wide hysteresis[J]. Journal of Materials Engineering,2004,(7):60.(王磊,闫德胜,姜志民,戎利建. Ni-Ti-Nb宽滞后形状记忆合金管接头研究和进展[J].材料工程,2004,(7):60.)
[4] Wang L M,Zheng Y F,Cai W,Wang Z,Zhao L C.Present research and application of Ni-Ti-Nb shape memory alloys with wide hysteresis in aerospace[J]. Aerospace Materials&Technology,2000,(3):5.(王利明,郑玉峰,蔡伟,王中,赵连城. NiTi-Nb宽滞后形状记忆合金研究进展及其应用[J].宇航材料工艺,2000,(3):5.)
[5] Yang G J,Deng J. Recent advances in the study of the Ti-Ni-Nb shape memory alloy with wide hysteresis[J].Rare Metal Materials and Engineering, 1998, 27(6):322.(杨冠军,邓炬. Ti-Ni-Nb宽滞后记忆合金的研究进展[J].稀有金属材料与工程,1998,27(6):322.)
[6] Simpson J A,Melton K,Duerig T. Method of processing a nickel/titanium-based shape memory alloy and article produced therefrom[P]. US Patent:4631094,1986.
[7] Uchida K,Shigenaka N,Sakuma T,Sutou Y,Yamauchi K. Effect of Nb content on martensitic transformation temperatures and mechanical properties of Ti-Ni-Nb shape memory alloys for pipe joint applications[J]. Materials Transactions,2007,48(3):445.
[8] He X M,Rong L J,Yan D S,Li Y Y. Ti Ni Nb wide hysteresis shape memory alloy with low niobium content[J]. Materials Science and Engineering A, 2004,371:193.
[9] Xiao F,Ma G,Zhao X,Xu H. Effects of Nb content on yield strength of Ni Ti Nb alloys in martensite state[J]. Chinese Journal of Aeronautics,2009,22:658.
[10] Liu W,Zhao X. Mechanical properties and transformation behavior of Ni Ti Nb shape memory alloys[J]. Chinese Journal of Aeronautics,2009,22:540.
[11] Jiang P C,Zheng Y F,Tong Y X,Chen F,Tian B,Li L,Gunderov D V,Valiev R Z. Transformation hysteresis and shape memory effect of an ultrafine-grained Ti Ni Nb shape memory alloy[J]. Intermetallics,2014,54:133.
[12] Xiao Y,Zeng P,Lei L P. Influence of peak stress on plastic behavior of Ni Ti shape memory alloy under cyclic deformation[J]. Journal of Plasticity Engineering,2017,24(1):145.(萧遥,曾攀,雷丽萍.峰值应力对Ni Ti形状记忆合金循环变形塑性行为的影响[J].塑性工程学报,2017,24(1):145.)
[13] Hamilton R F,Lanba A,Ozbulut O E,Tittmann B R.Shape memory effect in cast versus deformation-processed Ni Ti Nb alloys[J]. Shape Memory and Superelasticity,2015,1(2):117.
[14] Bewerse C,Brinson L C,Dunand D C. Microstructure and mechanical properties of as-cast quasibinary Ni Ti-Nb eutectic alloy[J]. Materials Science&Engineering A,2015,627(1):360.
[15] Zhang C S,Wang Y Q,Chai W,Zhao L C. The study of constitutional phases in a Ni47Ti44Nb9shape memory alloy[J]. Materials Chemistry and Physics, 1991,28:43.
[16] Piao M,Miyazaki S,Otsuka K,Nishida N. Effects of Nb addition on the microstructure of Ti-Ni alloys[J].Materials Transactions JIM,1992,33(4):337.
[17] Chen Y,Jiang H,Rong L,Xiao L,Zhao X. Mechanical behavior in Ni Ti Nb shape memory alloys with low Nb content[J]. Intermetallics,2011,19:217.
[18] Wang M,Jiang M,Liao G,Guo S,Zhao X. Martensitic transformation involved mechanical behaviors and wide hysteresis of Ni Ti Nb shape memory alloys[J].Progress in Natural Science:Materials International,2012,22(2):130.