Separation of the Martensite in TiNi Fiber Reinforced Aluminum Matrix Composite

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.     

Two-way shape memory effect of TiNi alloy coil extension springs

A two-way shape memory effect (TWSME) spring that could elongate upon heating and contract upon cooling was obtained by constrained annealing and thermo-mechanical training. The effect of heat treatment and thermomechanical training on the TWSME and the effect of training on the transformation temperatures had been studied by elongation-temperature, electrical resistance measurements and differential scanning calorimetry (DSC). The TWSME recovery rate of extension spring increases with increasing the training cycles and increases to a saturation value. The inverse martensitic and martensitic temperatures decreased with increasing thermo-mechanical training cycles.     

Repeatable temperature memory effect of TiNi shape memory alloys

An incomplete transformation cycle induces a kinetic stop in the following complete transformation cycle in TiNi shape memory alloys. The kinetic stop can be regarded as a memory of the previous interruption temperature. This memory was generally believed to be a one-time phenomenon. Herein, we show that the temperature memory effect is actually a long-lasting phenomenon. Experimental results show that a repeatable temperature memory effect can be introduced into a TiNi alloy by a deformation lager than 12%. Deformation induced dislocations are considered a main factor to the persistence of the memory. The memory becomes more distinct with increasing numbers of the incomplete thermal cycle, but the memory becomes less distinct with increasing numbers of subsequent complete transformation cycling.     

Martensitic Transformation of TiNi Shape Memory Alloy Fiber Reinforced Ni Matrix Composites

In this paper, a TiNi shape memory alloy fiber Ni matrix composite was fabricated by an electroplating method using TiNi alloy as the cathode and Ni as the anode. The constrained martensitic transformation behaviors of the TiNi alloy were studied by differential scanning calorimeter (DSC), and the results showed that two endothermic peaks appear on the DSC heating curves and the reverse transformation temperatures increase with increasing prestrain levels. Moreover, comparing to the free transformation, the temperature window of the constrained reverse transformation is widely expanded due to the influence of recovery stress.     

FeMnSiCrNiCo合金记忆性能的研究

针对具有良好耐蚀性的FeMnSiCrNiCo系合金 ,确定了合理的热加工及固溶处理温度 ,研究了预变形量、退火温度及记忆训练对合金记忆性能的影响 ,并分析了微观组织。结果表明 ,随着预变形量增加 ,记忆回复率 (ηm)下降 ,但记忆回复应变量 (εm)有一个最佳值。合金的记忆性能和微观组织随训练退火温度变化而不同 ,训练退火温度对训练效果起十分关键的作用 ,母相亚结构是决定合金记忆性能的根本因素     

TiNi形状记忆合金约束态相变及驱动特性研究进展

TiNi形状记忆合金作为一种驱动材料具有广阔的应用前景，同时TiNi合金丝增强复合材料的研究和应用也得到人们的重视。TiNi合金的驱动能力与其约束条件下的相变行为有密切的关系。综述了不同约束态条件下TiNi形状记忆合金丝的马氏体相变特征及其驱动特性的研究进展。     

TiNi合金在恒应力约束下的不完全相变

利用DSC对预应变TiNi形状记忆合金丝在恒应力约束下的马氏体不完全逆相变进行了研究,发现不完全相变热循环样品在第二次自由态加热过程中出现两步马氏体逆转变和两段应变回复现象.分析认为:经过恒应力约束下的不完全逆相变后,TiNi样品中存在不同的马氏体,在随后的加热过程中先后逆转变,产生两段回复应变.     

TiNi形状记忆合金的相变行为及其影响因素

对近年来有关ＴｉＮｉ形状记忆合金的相变行为及其影响因素等方面的最新研究成果综合评述，主要内容包括化学成分，应力／应变，热／机械循环，冷／加热和热处理制度等因素对相变温度和相变次序的影响。     

TiNi形状记忆合金的工程应用研究现状和展望

综合评述了TiNi形状记忆合金的特性及其在工程结构方面的应用研究进展.着重介绍了TiNi合金形状记忆效应和超弹性的特点及其工程意义,论述了TiNi合金在用于制作驱动器、控制结构变形和开裂、结构振动主动和被动控制以及在耐磨损、抗冲击方面的应用研究现状,并就该研究领域的发展方向提出了一些建议.     

TiNi形状记忆合金丝/水泥复合材料的相变行为

研究了TiNi形状记忆合金/水泥基复合材料的相变行为。差热分析(DSC)研究结果表明,由于水泥基体的约束作用,形状记忆合金中剩余取向马氏体的逆相变温度上升。在逆相变开始阶段,逆马氏体相变的平均速率较大;在复合材料DSC加热曲线吸热峰结束温度以上,剩余马氏体的逆相变仍在缓慢进行。     

不同方式预应变TiNi合金丝的马氏体逆相变温度

对恒应力约束下降温预应变和室温拉伸预应变TiNi形状记忆合金丝的马氏体逆相变行为进行研究.结果表明,随着预应变的增加,二者的马氏体逆相变温度都上升,应变回复率都下降;但是在相同预应变下,前者的马氏体逆相变温度低于后者,后者的应变回复率却高于前者.     

Microstructure characterization of the non-modulated martensite in Ni–Mn–Ga alloy

The microstructure of the non-modulated martensite in a Ni–Mn–Ga alloy has been characterized in detail by conventional transmission electron microscopy. Bright field images show that the martensite exhibits an internal substructure consisting of a high density of narrow twins. Using electron diffraction, it is found that the martensite has a tetragonal crystal structure. The lattice correspondence between the parent phase and the non-modulated martensite is investigated. Furthermore, the four twinning elements describing the microtwinning have been graphically and quantitatively determined. The results indicate that the microtwinning within the non-modulated martensite belongs to the compound type.     

Grain-size gradient NiTi ribbons with multiple-step shape transition prepared by melt-spinning

A grain-size gradient NiTi ribbon with multiple-step shape transition was papered by means of melt-spinning.The ribbons contain coarse and fine grains in the free surface side and copper roller surface side,respectively.The grain-size gradient microstructure induces a two-stage phase transformation behavior in the ribbons during heating or cooling.After tensile deformation pre-treatment,the ribbons exhibit a back-and-forth shape change (shape A→ B-A) upon a single heating or cooling process,resulting from the sequential phase transformation through the thickness of the ribbon as dictated by gradient grain size.The activating performance of the ribbons,i.e.shape transition amplitude and speed,can be customized by controlling the pre-deformation strain.This work offers a new opportunity for innovative designs to reach a novel shape memory behavior in NiTi alloys conveniently and efficiently.     

Study of incomplete transformations of near equiatomic TiNi shape memory alloys by DSC methods

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 R_f and M_s, the heat flow detected upon following heating only shows one endothermic peak. With decreasing the turn back temperature to a temperature between M_s and M_f, 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.     

电子辐照影响TiNi形状记忆合金R相变的研究

用能量为1.7MeV不同注量的电子辐射了TiNi形状记忆合金,通过温度控制使辐照在合金的R相状态进行,发现辐照使合金和奥氏体逆转变开始温度As和结束温度Af升高,随着辐量的增加有增大的趋势,且奥氏体转变滞后也有所增大,R相转变开始点Rs和转变结束点Rt略有增加。XRD结果表明电子辐射成了R相点阵畸变,随辐照注量的增加有增大的趋势。这一变化被认为是辐照引入的点缺陷导致了R相稳定化,并且部分缺陷打打扎了R相界面造成的。这一结果为记忆合金相变点的调节提供了新方法。     

TiNi记忆合金的马氏体相变与形状记忆效应

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。     

TiNi形状记忆合金连接技术的研究进展

TiNi形状记忆合金具有很多优异性能,在航空航天、原子能、海洋开发、仪器仪表以及医疗器械等领域具有广阔的应用前景,而TiNi形状记忆合金的连接技术是其实用化的关键技术之一.综述了TiNi形状记忆合金连接技术的发展现状,重点评述了TiNi形状记忆合金激光焊、固相焊和钎焊的研究状况,指出了需要深入研究的问题.     

Thermal analysis of the effect of aging on the transformation behaviour of Ti–50.9at.% Ni

This study investigated the effects of aging on the transformation behaviour of a Ti–50.9at.% Ni alloy by means of differential scanning calorimetry. It was found that aging at 673 K induced complex transformation behaviour, involving the R-phase and multiple-stage martensitic transformations. The martensitic transformations were analysed in details in partial transformation cycles. It was evident that the martensitic transformation from the R-phase occurred in a stable manner progressively over a wide temperature range. These evidences appear to support the precipitate inhomogeneity hypothesis for the explanation of multiple-stage martensitic transformations and disprove the hypothesis that martensitic transformations in near-equiatomic NiTi occur in burst manner.     

Ti-content and annealing temperature dependence of transformation behavior of TiXNi(92-XCu8 shape memory alloys

Ti-content and annealing temperature dependence of the transformation behavior of Ti_XNi_(92-X)Cu_8.0 (at,%) (X = 49.0–5l.0) alloys was investigated by varying the annealing temperature from 573 to 1273 K. It was found that the peak temperature of B2–B19 transformation (O^*) increases with increasing annealing temperature from 673 to 873 K for all of the alloys. With annealing at temperatures above 873 K, the influence of annealing on O^* depends on Ti-content. In the range of 50.4–51.0 at.% Ti, O^* shows little dependence on annealing temperature. In the range of 49.3–50.2 at.% Ti, O^* firstly decreases and then keeps constant with increasing annealing temperature. For the alloy of 49.0 at.% Ti, O^* continuously decreases with increasing annealing temperature from 873 to 1273 K. On the basis of the above data, a partial phase diagram of Ti-Ni-8.0Cu (at.%) was proposed. The transformation hysteresis also showed unique Ti-content and annealing temperature dependence.     

Martensitic transformation in zirconia containing ceramics and its applications

An introduction to tetragonal (t) → monoclinic (m) martensitic transformation in zirconia containing ceramics, especially tetragonal zirconia polycrystalline (TZP) was presented. Thermodynamics, crystallographics and kinetics of t → m martensitic transformation in TZP were emphasized. Transformation toughening and shape memory effect (SME) associated with t → m martensitic transformation in the TZP were reviewed. Perspective of future challenges was briefly mentioned at the end.