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In this work, we present a reduction procedure for 3D models describing phase transformations in copper-based shape memory alloys (SMAs) and develop a robust numerical algorithm for the computational analysis of thin single-crystal slabs of these alloys. Starting from a general Landau-type 3D model for the SMA dynamics we have developed a new mathematical “slow manifold” model that allows us to describe effectively the main features of the thermomechanical behaviour of CuAlNi alloys. Results of the mathematical modelling of the thermomechanical fields in CuAlNi SMAs are discussed with numerical examples. 相似文献
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This paper examines the effects of TiC and NbC precipitation and prior cold rolling on the shape memory behaviour of an iron-based alloy. A precipitate-free alloy was used as a reference to investigate the relative contributions of prior-deformation and precipitation on shape memory. Heat treatment of the Nb- and Ti-containing alloys at 700 °C and 800 °C resulted in carbide precipitates between 120 nm and 220 nm in diameter. Bend testing of these samples showed a marginal increase in shape memory compared to the precipitate-free alloy. Under these conditions TiC precipitation exhibited slightly better shape memory than for NbC. However, this small increase was over-shadowed by the marked increase in shape memory that can be produced by subjecting the alloys to cold rolling followed by recovery annealing. When processed in this way, fine carbides are formed in the Ti- and Nb-containing alloys during the heat treatment. For particles >25 nm in diameter the shape memory is unaffected, but, it was found that small <5 nm particles have a detrimental effect on shape memory due to pinning of the martensite plates, thereby inhibiting their reversion to austenite. The optimum shape memory was observed in the precipitate-free alloy after cold rolling and recovery annealing. 相似文献
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In Ni-Mn-X(X=In,Sn,Sb) ferromagnetic shape memory alloys,a ferromagnetic transition from paramagnetic to ferromagnetic austenite and a martensitic transformation from ferromagnetic austenite to weak magnetic martensite occur in some particular composition ranges,in which abundant physical properties have been observed by the abrupt change of magnetization and resistivity around their transition temperatures in these alloys.Therefore,tuning the martensitic transformation temperature(TM) and enlarging the workingtemperature interval for Ni-Mn-X(X=In,Sn,Sb) alloys,are of great importance.In the present paper,we will focus on the effect of external factors,including pre-deformation,annealing,and high pressure annealing,on the magnetic transitions and the related magnetocaloric properties in Ni-Mn-Co-Sn ferromagnetic shape memory alloys.Our approaches and the main results in this particular field will be reviewed. 相似文献
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综述了镍钛、铜基、铁基形状记忆合金,热致型、光致型、电致型、磁致型、化学感应型形状记忆高分子,以及形状记忆陶瓷的形状记忆机理、特性及其应用现状,并提出形状记忆材料的研究方向为:加强形状记忆合金的抗疲劳性能研究,建立一套统一的研究方法和合理的评价体系;加强形状记忆高分子材料的结构设计研究;改善陶瓷的形状记忆性能,以拓展形状记忆陶瓷的应用领域。 相似文献
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AbstractNiTiHf-based shape memory alloys have been receiving considerable attention for high temperature, high strength and two-way shape memory applications since they could have transformation temperatures above 100°C, shape memory effect under high stress (above 500 MPa) and superelasticity above 100°C. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf-based alloys have some drawbacks such as low ductility and high slope in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. It has been revealed that microstructural control is crucial to govern the shape memory properties (e.g. transformation temperatures, matrix strength, shape recovery strain, twinning type, etc.) of NiTiHf-based alloys. A summary of the most recent improvements on selected NiTiHf-based systems is presented to point out their significant shape memory properties, effects of alloying, aging and microstructure of transforming phases and precipitates. 相似文献
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Ni-Mn基磁性形状记忆合金具有良好的温度场和磁场诱发的形状记忆效应、超弹性、磁热效应、磁阻效应、弹热效应、交换偏置效应等功能特性。作为一种新型多功能材料,有望应用于驱动器、传感器等多个工程领域。本文详细阐述了包含第二相的Ni-Mn基磁性形状记忆合金的研究现状,梳理和总结了第二相的形成及其对马氏体相变、功能特性和力学性能的影响,提出了一些有待解决的问题,如第二相对包括磁性形状记忆效应在内的磁功能特性的影响,并指出未来应着重于研究第二相形成与演化过程的热力学/动力学因素,对第二相进行合理调控,从而优化合金功能特性。 相似文献
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本文综述了近年来有关高温形状记忆合金的最新研究进展。重点介绍了CuAlNi基,NiTi基及NiAl基三大系列高温形状记忆合金。概括了有关合金的设计,马氏体相变及形状记忆效应,显微结构特征,合金相稳定性及热处理效应,材料制备及生产加工工艺及性能等。 相似文献
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In many applications, shape memory alloys are being replaced by shape memory polymers as they have some better properties than shape memory alloys. Nevertheless, shape memory alloys can recover under load which shape memory polymers cannot. Shape memory polymers are not capable of giving full recovery even lifting a tiny load. The melting temperature or the glass transition temperature is the transition temperatures to which shape memory polymers are closely heated. Then a deforming force up to a certain position is applied to the heated shape memory polymers. After that shape memory polymer is permitted to cool while keeping it deformed. After the cooling, shape memory polymer obtains the temporary shape which can be recovered by reheating it at the similar transition temperature (glass transition or melting). Consequently, it recovers at its initial state. Shape memory polymer can achieve constrained recovery and unconstrained recovery, nonetheless; under stress, it is partly recovered. In current work, recovery under load has been investigated of an asymmetrical shape memory composite. It is established that it is capable to recover under various loads. Under various loads, it shows full recovery in reference to initial state. The ability to recover under load can be potentially used in diverse applications. 相似文献