磁性形状记忆合金研究进展

磁性形状记忆合金是上世纪90年代开始出现的一类新型金属功能材料。这类合金兼具热弹性马氏体相变和磁性转变,其形状记忆效应可以由磁场控制。此外这类合金还具有磁阻、磁热等丰富的物理效应,因而一直是近期研究热点。首先介绍了磁性形状记忆合金的3个基本特征,即马氏体相变与磁性转变、磁场驱动孪晶再取向和磁场诱发相变。然后分别对Ni基、Co基和Fe基磁性形状记忆合金的研究现状进行了评述。最后展望了磁性形状记忆合金的发展趋势。     

磁控形状记忆合金在结构振动控制中的应用研究

磁控形状记忆合金(MSMA)是一种在磁场控制下可产生较大变形,且具有形状记忆功能的新型智能材料,利用其磁控特性可以制作智能作动器进行结构的振动控制。首先介绍了MSMA材料在磁场作用下的变形机理与磁控特性,在此基础上提出了两种可以应用于结构振动控制中的新型MSMA驱动器,并分析了其工作原理和设计方法,最后阐述了利用MSMA的逆特性制作MSMA自传感作动器的关键技术及解决方法,为其在土木工程领域的应用打下了良好的基础。     

Magnetic Interactions in Ni‐Mn‐Based Magnetic Shape‐Memory Heusler Alloys

Ni‐Mn‐based Heusler alloys exhibit a variety of features related to martensitic transformations and are materials that are sought to be employed in actuation applications. To be able to exploit their properties, it is necessary to understand the rich variety and subtle magnetic coupling mechanisms occurring in these alloys. We review complementary neutron polarization analysis and ferromagnetic resonance experiments and give an account on the complex magnetism of these alloys in the austenite and martensite states.     

Phase Change Behavior of Nitinol Shape Memory Alloys

Among other special characteristics Shape Memory Alloys (SMAs) have the ability to return to a predetermined shape when heated. In fact, the phase change of an existing element can strongly be influenced by thermal and thermo‐mechanical treatments. Up to now, SMEs have been discovered in various materials, which can generally be classified into noble‐metal based, Cu‐based, Fe‐based, Ni‐Ti‐based alloy systems and non‐metallic SMAs. In this paper a general overview of the Ni‐Ti system and a detailed review over the Ni‐Ti‐Cu system will be given with special regard to the influence of heat treatments upon the phase change behavior.     

PM‐Composites with Nickel‐Titanium Shape Memory Alloys

Starting from NiTi‐powders, composites of nickel‐titanium shape memory alloys (NiTi‐SMA) and different stainless steels as well as of different NiTi‐SMAs were produced by using the process of hot isostatic pressing (HIP). Metallographic investigations focussed on the interface between NiTi‐SMA and stainless steel with special emphasis placed on the characterization of the typical structure of the diffusion zones in both components.     

磁控形状记忆合金Co-Ni-Al的研究进展

介绍了Co-Ni-Al磁控形状记忆合金的晶体结构及特点,综述了近年来国内外Co-Ni-Al合金在热处理工艺、合金化以及磁控形状记忆效应方面的研究现状,指出了Co-Ni-Al磁控形状记忆合金目前存在的问题及今后发展的方向。     

A First‐Principles Investigation of the Compositional Dependent Properties of Magnetic Shape Memory Heusler Alloys

The interplay of structural and magnetic properties of magnetic shape memory alloys is closely related to their composition. In this study the influence of the valence electron concentration on the tetragonal transformation in Ni₂Mn_{1 + x}Z_{1 ? x} (Z = Ga, In, Sn, Sb) and Co₂Ni_{1 + x}Ga_{1 ? x} is investigated by means of ab initio calculations. While the type of magnetic interaction is different for the two series, the trends of the total energy changes under a tetragonal transformation are very similar. We find that tetragonal structures become energetically preferred with respect to the cubic one as the valence electron concentration e/a is increased regardless of the system under consideration. In particular, the energy difference between the austenite and martensite structures increases linearly with e/a, which is in part responsible for the linear increase of the matensite transformation temperature. The substitution of nickel by platinum increases even further the transformation temperature.     

Principle Design of Actuators Driven by Magnetic Shape Memory Alloys

Magnetic shape memory alloys (MSMA) are a promising material for actuation purposes as they provide relatively large strains and relatively high operation frequencies. In this paper three concepts of such actuators are introduced. The first part will describe a so called spring actuator, where the MSM element is working against a restore pre‐stress spring. The second concept uses two MSM elements working antagonistically to substitute the pre‐stress spring. A small sized actuator for valve or switching applications is shown in the third concept. Advantages and disadvantages are highlighted and show the potential of the comparatively new active material.     

The Role of Adaptive Martensite in Magnetic Shape Memory Alloys

Magnetic shape memory materials require a high twin boundary mobility and low hysteresis for applications mainly as actuators, sensors, and magnetocaloric cooling elements. Usually, outstanding properties are found only in samples with a modulated martensitic structure. Here, we analyze the question why a modulated structure is beneficial and show evidence that the modulated martensite is not an equilibrium phase but a nanoscale microstructure of non‐modulated (NM) martensite. In this review, we combine results from continuum and atomistic theory, as well as local and integral measurements on the model system Ni–Mn–Ga. Following the concept of adaptive martensite the modulated phase forms to minimize elastic energy near the phase boundary by introducing low‐energy twin boundaries between lamellae of the NM martensite that have widths of a few unit cells.     

Prediction of Phase Diagrams for Hard Materials: Application to Boron Crystals

Hard materials and refractory materials, such as diamond, are generally stable and have high melting points. The phase diagrams of these materials seem to be relatively simple. However, recent progress of high-pressure experiments along with theoretical predictions by density-functional theoretical (DFT) methods has disclosed the richness of new structures, which has attracted the attention of material researchers. An elemental crystal of boron is an extreme case; there are many polymorphic modifications, and it is only recently that the phase diagram has been established. In the course of studying the phase diagram, a new structure of the \(\gamma \) -phase has been discovered. Now, we have to admit that hard materials are rich sources for materials research. Many metastable phases are hidden behind the widely accepted phase diagrams. How to discover these hidden phases is one of the central issues for materials research. In this paper, experiences with predicting the phase diagram of boron by a theoretical approach are described and impacts on materials research, by taking superconductivity research as a working example, are shown. A combination of the microscopic method of DFT and the macroscopic approach of thermodynamics is an extremely powerful tool.     

Fe-Mn-Si系形状记忆合金研究近况

Fe-Mn-Si系形状记忆合金因其很好的可加工性和低廉的价格而备受关注.综述了该系形状记忆合金最近的研究工作,包括相变机制、影响因素,着重是提高和改善Fe-Mn-Si系合金性能的途径.主要通过选择合适的合金成分配比和摸索恰当的制备工艺来提高和改善Fe-Mn-Si系合金性能,叙述了该合金系不同合金元素和制备工艺对形状记忆效应的影响.     

新型磁驱动形状记忆合金研究进展

磁驱动形状记忆合金是一种新型功能材料,由于兼具大的输出应变和高响应频率等综合特性,成为智能材料领域的研究热点之一.本研究首先总结了Ni-Mn-Ga合金在相变和磁致应变性能方面的特点,然后着重介绍了Co-Ni-Ga和Ni-Fe-Ga两类新型磁驱动记忆合金在结构、相变、形状记忆效应、磁性能等方面的研究进展,并对其中存在的问题进行了讨论.     

Fe-Mn-Si基形状记忆合金在管接头方面的研究及应用

回顾了形状记忆合金的发展历史,阐述了Fe-Mn-Si基形状记忆合金的形状记忆机制及其管接头的连接原理,分析了Fe-Mn-Si基形状记忆合金在价廉管接头方面的研究现状,并提出了在这一研究热点中尚待解决的问题.     

TiNi基高温形状记忆合金的马氏体相变与形状记忆效应

综述了Ti-Ni基高温形状记忆合金中的马氏体相变和形状记忆效应最近研究进展。Ti-Ni基高温形状记忆合金主要包括用Ti-Ni-Pd,Ti-Ni-Pt,Ti-Ni-Zr和Ti-Ni-Hf等。对Ti-Ni基高温形状记忆合金体材料、薄带和薄膜中的马氏体相变、组织结构、形状记忆效应以及超弹性性能等进行了评述和归纳。值得注意的是,通过适当的时效处理可调节相变温度,显著改善Ti-Ni-Hf高温形状记忆合金的开头记忆效应和超弹性性能,其主要原因在于时效的Ti-Ni-Hf合金中析出纳米级析出相导致基体强度升高。采取适当的制备和加工方法,提高合金的马氏体相变温度,改善合金的开头记忆效应,是当前TiNi基形状记忆合金研究的主要发展趋势。     

Martensitic Transformation in Fe-Mn-Si Based Shape Memory Alloys

1.IntroductionFe-Mn-Sibasedalloysbecomeonekindofim-portantshapememorymaterialssincethecompleteshapememoryeffect(SME)waJsfoundinFe-3OMn-1Sialloyresultedfromfcc(7)-+hcp(E)martensitictransformationin1982bySatoet.1.[i].WorksonfCc(7)-+hcp(E)havebeenextensivelypublishedinlasttenyears.Thepresentauthorhaspointedoutsomenewaspectsoffcc(7)-hcp(E)transformationinalloyswithlowstackingfau1tenergyandhasanalyzedtheSMEassociatedwithfcc(7)-hcp(E)transformationinFe-Mn-Sibasedalloys[2~4].Thispaperattempt…     

铁磁性形状记忆合金CONiAl的磁性和输运性能研究

用电孤熔炼法制备了CoxNi71-xAl29（x=35、36、37）系列合金，并用甩带法对其进行退火。X射线能谱揭示三个样品均为单相样品。在升温过程中，CoxN71-xAl29系列合金发生了从马氏体→奥氏体的转变，而在降温过程中则发生奥氏体→马氏体的转变。输运性能测量显示，CoxNi71-xAl29出现了正的磁电阻，最大磁电阻可达到12．3％。     

Cu-AI-Ni形状记忆合金的超弹性和应力诱发相变

本文对多晶 Cu-Al-Ni 形状记忆合金进行了力学行为和应力诱发相变的研究。测定了在各种循环下的应力-应变曲线并进行了比较。x-射线衍射结果表明,在低于 Ms 点和高于 A_f 点变形时,分别发生了β_1→γ_1′和β_1→β_1′的诱发相变,并伴有β_1′马氏体的再取向。     

热处理对NiTi形状记忆合金的相变的影响

对含Ti 50.8%的NiTi形状记忆合金在300℃、400℃、500℃保温不同时间进行时效处理,然后通过差示扫描量热仪DSC对其相变温度点进行测定,发现经时效处理调节后,Af最大可下降20~30℃左右,而Ms变化不大。通过不同时效温度和保温时间的DSC曲线比较,得出热处理对其相变温度点的影响规律,即在300~500℃时效处理时,保温时间越短,Af降低越明显,在相同保温时间时,保温温度越低,Af降低越明显。     

Drilling of NiTi Shape Memory Alloys

The machinability of NiTi based shape memory alloys has been examined by conducting drilling experiments. For this reason the cutting parameters cutting speed and feed were varied within a wide range. The machining process was evaluated in terms of tool wear, cutting forces and machining quality. The tool wear was analysed with a scanning electron microscope and the influence of machining on the subsurface zone was evaluated by micro hardness measurements.