共查询到20条相似文献,搜索用时 140 毫秒
1.
《材料导报》2020,(3)
形状记忆合金凭借其独特的形状记忆效应和超弹性成为了重要的金属智能材料,在航空航天、电子、汽车和医疗等领域展现出巨大的应用价值。二元近等原子比镍钛合金是最为成熟的形状记忆合金材料,但是镍钛合金难以在很高的温度环境下(100℃,373 K)实现应用。以航空航天、核反应堆等为代表的高温服役环境迫切需要具有高相变温度(373 K)且综合性能良好的形状记忆合金,因此,发展高温形状记忆合金是本领域面临的研究重点和难点。近年来,科研工作者们以新型钛基合金为研究对象,通过合金化元素设计,获得具有高马氏体相变温度的形状记忆材料,发展出Ti-Ta基、Ti-Zr基、Ti-Nb基、Ti-Mo基等新型高温形状记忆合金体系。在满足高温相变特性的基础上,这些合金体系体现出不同的性能特点,例如Ti-Ta基合金利用Ta元素有效抑制ω相的析出而提高合金塑性,Ti-Nb基合金具有良好的加工成型能力。此外,以Pd、Pt、Au等贵金属为合金化元素可以进一步提高材料的相变温度,加入Sn、Al、Ga等元素则可以适当降低相变温度,并改善材料的力学性能和功能特性。本文综述了Ti-Ta基、Ti-Zr基、Ti-Nb基、Ti-Mo基等主要钛基高温形状记忆合金体系的研究进展,着重分析了合金化元素对合金相变温度、形状记忆效应、力学性能的影响规律,对各类合金的性能优势及缺点进行了全面总结,提出了高温形状记忆合金研究中存在的问题和未来发展方向。 相似文献
2.
3.
4.
5.
考虑相变的TC4钛合金流动应力研究 总被引:1,自引:0,他引:1
为完善TC4钛合金的塑性成形理论,必须建立准确的流动应力模型,而TC4钛合金的流动应力不仅与温度、应变速率和应变量相关,也受到βα+β相变的影响.本文通过等温实验和DSC实验研究了900℃时TC4钛合金的等温与连续冷却过程中的相变动力学,建立了相变动力学模型;通过Gleeble 3800热模拟机进行热压缩实验,根据实测的TC4钛合金在高温β区与低温α+β区的流动应力曲线,建立了流动应力模型;将相变动力学模型与流动应力模型结合,建立了考虑相变的流动应力模型;最后将TC4钛合金在900℃等温不同时间后进行压缩变形,对比实验得到的流动应力曲线与模型计算得到的流动应力曲线,验证了该模型的准确性. 相似文献
6.
目的获得一种低成本钛合金Ti12LC准确的相变点。方法采用差热分析法和连续升温金相法,对钛合金的相变温度进行了测定。首先通过差热分析,初步确定了该钛合金相变温度范围,接着采用连续升温金相法,进一步精确分析钛合金的相变点。通过分析DSC曲线中的吸热、放热现象,对该合金的相变温度范围进行研究,再通过试样淬火后的金相分析,研究α相和β相的数量及分布。结果确定了Ti12LC钛合金的相变温度在880~890℃之间,而连续升温淬火金相法测得Ti12LC钛合金的相变温度为885℃。结论由于淬火温度间隔小,两种分析方法下,该相变温度的测定较为准确。 相似文献
7.
8.
9.
根据钛合金的相变理论,建立了β型钛合金材料相变温度的新测试方法。首先对合金试样进行预热处理,在理论相变温度以上30~50℃保温40min炉冷至650℃后空冷。然后按照GB/T 23605-2009测试相变温度,晶界板条α体积分数小于1%和等于0%的温度区间即为β型钛合金相变温度区间。TC18,TB6,TB3,TB8钛合金相变温度的测试结果表明该方法切实可行,弥补了标准测试法方法的不足。 相似文献
10.
11.
The ω phase is commonly observed in β-Ti alloys and plays a significant role on various properties of β-Ti alloys.Although many results about the role ofω phase on mechanical properties of β-Ti alloys have been derived from theoretical and experimental studies,the role ofω phase on deformation mechanism hitherto remains elusive and deserves to be further studied.In this work,the role played by ω phase during the {112 } <111>β twinning in Ti-Mo alloys were investigated by first-principles calculations at atomic scale.In the energy favorable interface of(112)β/(10(1)0)ω,we found that partial dislocations slipping on the successive (10(1)0)ω planes ofω phase can lead to the formation of { 112} <111>β twin nucleus.And the twin nucleus grows inwards ω grain interior through atomic shuffle.Thus,a new twinning mechanism of {112 } <111>β assisted by ω phase was proposed.Furthermore,our calculations indicated that the Pearance of ITB (interfacial twin boundary) ω phase can improve the stability of the symmetrical 12 } <111 >β twin boundary (TB),which can well explain the experimental phenomenon that the ITB ω phase always accompanies the formation of {112 } <111>β twin.Finally,a probable microstructure evolution sequence was suggested,namely β matrix → β matrix + athermal ω phase → (112)[11(1)]twin → (112)[11(1)]β twin + ITB ω phase.Our calculations provide new insights on the role played by ω phase during the twinning process of {112} <111>β,which can deepen the understanding on the deformation behaviors of β-Ti alloys. 相似文献
12.
V Seetharaman 《Bulletin of Materials Science》1984,6(4):703-716
The influence of applied stresses and imposed plastic deformation on the martensitic transformation of a parent phase is described.
Changes in mechanical properties such as flow stress, work hardening rate, fracture toughness, etc brought about by strain-induced
martensitic transformation are briefly examined. In the absence of appreciable dislocation glide, atomic displacements associated
with glissile boundaries are highly ordered and reversible modes of (plastic or nonlinear pseudoelastic) deformation. Such
processes lead to large strains and are encountered in deformation twinning, martensitic transformations and in the reorientation
of martensite units. The reversibility leads to phenomena such as elastic twinning, thermoelastic martensites, superelasticity,
shape memory and two-way shape memory effects, and rubber-like behaviour. These are discussed using a unified approach based
on thermoelastic equilibrium. The shape memory effect suggests several potential applications of the martensitic transformations
in non-ferrous alloys in which the effect is most commonly observed. Recent developments in this area are reviewed with special
reference to the prerequisites for the effect and the influence of metallurgical processing on the extent of shape recovery. 相似文献
13.
In spinal fixation devices, the Young's modulus of the metallic implant rod should be not only sufficiently low to prevent stress shielding for the patient but also sufficiently high to suppress springback for the surgeon. This paper proposes a novel function of biomedical titanium alloys—self-adjustment of Young's modulus. Deformation-induced ω phase transformation was introduced into β-type titanium alloys so that the Young's modulus of only the deformed part would increase during operation, while that of the non-deformed part would remain low. The Young's modulus increase by deformation was investigated for a binary Ti-12Cr alloy. This alloy successfully underwent deformation-induced ω phase transformation and exhibited the increase in the Young's modulus by deformation. 相似文献
14.
Compression tests were performed to clarify the effects of transformation modes on the anomalous yield behaviour of hypo- and hyper-stoichiometric Fe3Al alloys which show a first- and a second-order transition, respectively. There were great differences in the anomalous yield behaviour depending on the transformation modes. In the first-order transformation alloy, changes in the degree of order played an important role before phase separation, while precipitation of phase had a great influence on the anomalous behaviour after phase separation. In contrast, only the change in the degree of order was a dominant factor in the second-order transformation alloy. 相似文献
15.
通过低温DSC测试仪、金相显微镜和拉伸试验机,研究NiTi形状记忆合金冷轧变形量对马氏体相变行和形状恢复率的影响。结果表明:冷轧变形生成的应力诱发马氏体和取向不同的丝织构及高密度位错,使得马氏体相变时界面迁移的阻碍作用增加,抑制了相变的发生;随冷轧变形量的增大合金的形状恢复率降低。 相似文献
16.
An investigation of the phase transformations experienced by the decagonal and icosahedral phases in two different quaternary alloys is carried out. The transformation in the decagonal phase of Al-Cu-Co-Si alloy is induced by the electron radiation in a transmission electron microscope. However, in the icosahedral phase of Al-Cu-Co-Fe alloy this transformation is induced by annealing. Electron diffraction patterns obtained from both phases suggest that the deformation mechanism involved in these kinds of transition is related to twinning. 相似文献
17.
K. Hackl W. Zhang M. Schmidt‐Baldassari U. Hoppe 《Materialwissenschaft und Werkstofftechnik》2004,35(5):284-288
The asymmetry associated with martensitic transformations observed in tension/compression experiments of shape‐memory‐alloys (SMAs) is investigated on the basis of a recently suggested micromechanical model. The approach is based on crystallographic theory and utilizes a framework of energy minimization in a finite deformation context. Polycrystalline NiTi under tension demonstrates smaller phase‐transformation start‐strain, differe phase‐transformation stress‐levels and flatter phase‐transformation stress‐strain slopes than that under compression in our numerical simulation. The phase‐transformation start‐stress is followed to have a linear relationship with respect to the temperature within a certain range. These results agree well with experimental results reported in the literature. 相似文献
18.
Andreas Stark Arno Bartels Helmut Clemens Sascha Kremmer Frank‐Peter Schimansky Rainer Gerling 《Advanced Engineering Materials》2009,11(12):976-981
Texture formation was studied in an intermetallic Ti‐45at%Al‐5at%Nb alloy after uniaxial compression and near conventional forging. Depending on the deformation conditions the texture of the γ‐TiAl phase is formed by pure deformation components, components related to dynamic recrystallization, or transformation components. This changing corresponds with microstructural observations. The α2‐Ti3Al and the α‐Ti(Al) phase show a similar texture as it is known for Ti and Ti‐base alloys after compressive deformation at elevated temperatures. In contrast to the γ texture, no significant change of the α/α2 texture was observed in the temperature range between 800 °C and just below the α‐transus temperature (Tα = 1295 °C). 相似文献
19.
Ti–Nb–Ta–Zr system alloys are receiving more attention for biomedical material component applications. However, the deformation behavior of the Ti–Nb–Ta–Zr system has not been evaluated to date. Therefore, the deformation behavior of Ti–Nb–Ta–Zr alloys with different Nb contents was investigated in this study.The behaviors of loading–unloading stress–strain curves of Ti–20Nb–10Ta–5Zr and Ti–25Nb–10Ta–5Zr air-cooled after final heating of the manufacturing process are similar to that obtained in metastable β type titanium alloys that have the shape memory effect. Therefore, the shape memory effect was expected in Ti–20Nb–10Ta–5Zr and Ti–25Nb–10Ta–5Zr alloys. The elastic deformation of Ti–30Nb–10Ta–5Zr disobeyed Hooke's law. However, stress or strain-induced martensite (SIM) is not observed on the loading–unloading stress–strain curve. The deformation mechanism of Ti–25Nb–10Ta–5Zr changes with varying its microstructure. In Ti–25Nb–10Ta–5Zr air-cooled after final heating, the microstructure consisted of an ω phase in a β phase. The stress for inducing martensite in a β phase, σM, was nearly equal to the yielding stress, σy. Therefore, stress-induced martensitic transformation and movement of dislocations occurred together. In Ti–25Nb–10Ta–5Zr water-quenched after final heating of the manufacturing process, the microstructure consisted of a single β phase, where σM is lower than σy. Therefore, stress-induced martensitic transformation occurred before yielding. 相似文献