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《Materials Letters》2001,47(4-5):286-289
A two-stage strain recovery was observed in a TiNi alloy fiber, which had been prestrained and experienced a constraint heating and cooling cycle with a fixed strain constraint. The results of differential scanning calorimeter (DSC) measurements showed that after the thermomechanical process, the self-accommodation martensite in the TiNi alloy was divided into two sorts of martensite, the redeformed martensite and the inheriting deformation martensite. The first stage of the recovery strain vs. temperature curve corresponds to the transformation from the inheriting deformation martensite to parent, and the second one corresponds to the transformation from the redeformed martensite to parent. 相似文献
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用激冷甩带法制备了Til-xNix(x=45%~49.8%)(原子分数)形状记忆合金(SMA)薄带,用示差扫描量热仪研究了Ni含量对铸态及450℃、500℃退火态TiNi SMA薄带相变行为的影响.结果表明,冷却/加热时,铸态和退火态Ti1-xNix(x=45%~49%)SMA薄带发生A→M/M→A一阶马氏体相变;当Ni含量为49.8%时,铸态和退火态TiNi SMA薄带冷却时发生A→ R→M两阶段相变,加热时发生M→A一阶段相变.随Ni含量增加,TiNi SMA薄带马氏体正、逆相变温度范围先增大后减小,Ni含量为48%时相变温度范围最宽.退火态比铸态TiNi SMA薄带相变温度范围窄.随Ni含量增加,TiNi SMA薄带马氏体正、逆相变温度升高,相变热滞增大.当Ni含量为49%时,SMA薄带的马氏体相变温度达最大值,当Ni含量为49.8%时马氏体相变温度迅速下降. 相似文献
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An incomplete thermal cycle upon heating in a shape memory alloy (arrested at a temperature between As and Af) induced a kinetic stop in the next complete thermal cycle. The kinetic stop temperature is closely related to the previous
arrested temperature. This phenomenon is named temperature memory effect (TME). In this article, the TME in two-way shape
memory TiNiCu and TiNi springs was investigated by performing either a single incomplete cycle, or a sequence of incomplete
cycles. N points of temperatures could be memorized if N times of incomplete cycles on heating were performed with different arrested temperatures in a decreasing order. The capability
is enhanced by performing repetitive incomplete cycles with the same temperature, and the TME can be eliminated by appropriate
complete transformation cycle. The TME is originated from the relaxation of both the strain energy between martensite and
coherent strain between parent phase and martensite. 相似文献
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冷轧变形对TiNi合金阻尼特性的影响 总被引:2,自引:0,他引:2
为了探讨冷轧变形对TiNi合金阻尼特性的影响,及TiNi合金马氏体的阻尼特性与组织结构之间的关系,采用示差扫描量热分析、透射电镜分析、动态机械分析和音频阻尼测试方法,系统研究了冷轧变形后Ti50Ni50合金马氏体的阻尼特性.研究结果表明:低频和音频时,Ti50Ni50合金马氏体的阻尼值随着冷轧变形量的增加呈现先增加而后降低的趋势,且音频时热马氏体和冷轧变形后马氏体的阻尼值较低频时的阻尼值均有大幅度地下降;冷轧后马氏体的高阻尼不仅与界面运动有关,也与马氏体中的缺陷有关. 相似文献
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承受各种循环加载的TiNi形状记忆合金的超弹性变形行为 总被引:6,自引:0,他引:6
TiNi形状记忆合金由于其优良的机械性能、抗腐蚀能力和生物适应性得到广泛的使用。超弹性是TiNi形状记忆合金重要的力学性能之一。本文通过实验研究了不同加载速率和不同实验温度下承受完全循环加载以及部分加载卸载的TiNi形状记忆合金超弹性变形行为。分析了循环变形期间马氏体相变应力和弹性模量变化的特性。研究表明在完全循环加载过程中,由于残余应变的存在,马氏体相变应力随循环增加而减小。马氏体相变应力的变化量(即残余应力)与残余应变成线形关系。对于受过循环变形的机械训练的TiNi形状记忆合金,研究了部分加载和卸载情况下其超弹性变形,分析了相变开始与结束的应力特性。 相似文献
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研究了约束态加热过程中产生的回复力对TiNi形状记忆合金剩余马氏体的影响.结果表明,产生的回复力使剩余马氏体发生了塑性变形,使逆相变温度升高,剩余马氏体分数和其逆相变温度之间存在特定的函数关系.但是,外部约束条件的变化对马氏体的自拉伸过程所造成的剩余马氏体分数与其逆相变温度之间的关系影响很小. 相似文献
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TiNi记忆合金的马氏体相变与形状记忆效应 总被引:5,自引:1,他引:4
对近些年来有关TiNi记忆合金中马氏相变和形状记忆效应的最新研究成果进行综合评述。主要内容包括马氏体的形成,相变晶体学和变体自协作以及变形行为和形状记忆效应。 相似文献
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奥氏体动态再结晶组织对马氏体相变的影响 总被引:1,自引:0,他引:1
采用电阻测量和X射线衍射分析方法,研究了Fe-32Ni合金高温变形奥氏体动态再结晶组织对马氏体相变开始温度Ms点和一定深冷处理温度下马氏体生成量的影响。与静态再结晶组织相比,动态再结晶晶粒组织不均匀,其位错亚结构也不均匀。具有位错密度梯度分布的成长中的动态再结晶晶粒晶界附近含有少量的易移动位错,促进马氏体的形核,提高Ms点及其Ms点以下较高温度区域墨迹初期的马氏体生成量,但是对于较低温度区域转变后 相似文献
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M. Villa M. F. Hansen K. Pantleon M. A. J. Somers 《Materials Science & Technology》2015,31(1):115-122
The austenite to martensite transformation in a semi-austenitic stainless steel containing 17 wt-%Cr, 7 wt-%Ni and 1 wt-%Al was investigated with vibrating sample magnetometry and electron backscatter diffraction. Magnetometry demonstrated that, within experimental accuracy, martensite formation can be suppressed on fast cooling to 77 K as well as on subsequent fast heating to 373 K. Surprisingly, martensite formation was observed during moderate heating from 77 K, instead. Electron backscatter diffraction demonstrated that the morphology of martensite is lath type. The kinetics of the transformation is interpreted in terms of athermal nucleation of lath martensite followed by thermally activated growth. It is anticipated that substantial autocatalytic martensite formation occurs during thermally activated growth. The observation of a retardation of the transformation followed by a new acceleration during slow isochronal (i.e. at constant rate) cooling is interpreted in terms of the combined effect of the strain energy introduced in the system during martensite formation, which thermodynamically and/or mechanically stabilises austenite, and autocatalytic nucleation of martensite. 相似文献
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The incomplete transformations of near equiatomic TiNi shape memory alloys were investigated by differential scanning calorimeter (DSC). The results showed that the incomplete transformation can induce multistage phase transformation in a sample showing R-phase transformation, when the turn back temperature located in a value between Rf and Ms, the heat flow detected upon following heating only shows one endothermic peak. With decreasing the turn back temperature to a temperature between Ms and Mf, two endothermic peaks (multistage phase transformation) can be observed upon the following heating. There were no incomplete transformation induced multistage phase transformations in a sample without R-phase transformation. 相似文献
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Yanjun ZHENG Lishan GUIDepartment of Materials Science Engineering University of Petroleum Beijing ChinaYan LIDepartment of Materials Science Engineering Beijing University of Aeronautics Astronautics Engineering Beijing ChinaDazhi YANGDepartment of Materials Engineering Dalian University of Technology Dalian China 《材料科学技术学报》2004,20(4):390-394
The reverse martensitic transformation of TiNi shape memory alloy fibers embedded in a pure aluminum matrix was studied in this paper. Results showed that the phase composition of the TiNi alloy fibers prior to prestraining at the room temperature had a significant influence on the differential scanning calorimetry (DSC) results of the composites. By a comparison to the high temperature X-ray diffraction (XRD) results, it was confirmed that the martensite was divided into two groups: the self-accommodating martensite (SAM) and the preferentially oriented martensite (POM). The evolving process of the separation of martensite was discussed. 相似文献
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采用示差扫描热分析(DSC)、X射线衍射(XRD)和扫描电子显微分析(SEM)等方法,研究了预应变对铝基体中复合的TiNi形状记忆合金丝的马氏体逆相变的影响.结果表明,预应变的TiNi丝发生两种逆相变,一种是热致马氏体(TIM)的逆相变,另一种是应力诱发马氏体(SIM)的逆相变.预应变样品的TIM逆相变的起始温度与未预应变样品的基本相同.SIM逆相变的起始温度随预应变的增大而升高.TIM和SIM逆相变的分数随预应变的增大而减少. 相似文献
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An electron-microscopical investigation of the morphology of equiatomic TiNi martensite has revealed at least two types of martensite: the twinned plate martensite and a wavy martensite. To our knowledge the latter has never been reported in the literature before. In a thin foil, the plate martensite can be transformed into the wavy martensite within a few weeks at ambient temperature or by temperature cycling between +100° C and liquid nitrogen temperature. The transformation into the wavy martensite has been studied dynamically with the aid of a video-recording system attached to the microscope. This revealed the step-wise migration of the irregular boundary between the wavy martensite and the high temperature phase. The transformation from the B2 phase to the wavy martensite is preceded by the formation of a superstructure having three times the lattice parameter of the CsCl (B2) structure. The transformation is very sensitive to the cooling rate during temperature cycling and can even be totally suppressed if the cooling rate is too high. The transformation characteristics are not affected by the thermal history of the sample. 相似文献
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In the present work, the effect of pre-strain on martensitic transformation of Ni43Mn43Co7Sn7 (at.%) alloy was investigated. The results show that Ni43Mn43Co7Sn7 alloy undergoes a martensitic transformation at 288 °C upon cooling. The thermal cycling does not affect the transformation behavior of the alloy, indicating the good thermal stability. The reverse transformation of the deformed martensite is pre-strain dependent. When the pre-strain is higher than 7.5%, the reverse transformation occurs in two-stage manner upon first heating due to the nonuniform martensite deformation. In contrast, during the first martensitic and second reverse transformation, the pre-strain shows little effect on the transformation temperatures. 相似文献
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Maciej Motyka Anna Baran-Sadleja Jan Sieniawski Malgorzata Wierzbinska Kamil Gancarczyk 《Materials Science & Technology》2019,35(3):260-272
ABSTRACTThe process of martensitic α′(α″) phase decomposition in titanium alloys has not been sufficiently characterised in the literature – especially in terms of plastically deformed martensite. The research results of water-quenched Ti–6Al–4V alloy, subsequently cold deformed in compression test and tempered at the temperature range of 600–900°C for 1 and 2?h were presented in the paper. Light and scanning electron microscopy observations revealed the influence of plastic deformation on tempered martensite laths morphology – particularly at the temperature of 900°C – it favoured their fragmentation and spheroidisation. The effect of plastic deformation on characteristic temperatures of α′(α″)→α?+?β phase transformation, phase composition and alloying elements distribution in phase constituents of Ti–6Al–4V alloy was identified and evaluated too.This paper is part of a thematic issue on Titanium. 相似文献