一种新型功能晶体Ni2MnGa

Ｎｉ_２ＭｎＧａ晶体同时具有强铁磁性、大磁致伸缩、温控和磁控形状记忆效应，其磁控形状记忆效应的响应频率接近压电陶瓷，输出应变和应力接近温控形状记忆合金，是近年来发现的一类新型功能晶体．Ｎｉ_２ＭｐＧａ晶体７７Ｋ时在［００１］方向，仅２ＭＰａ的预应力即可产生５％的温控可回复应变，已接近 ＴｉＮｉ合金 ６％～８％的可回复应变量；非化学剂量的 Ｎｉ。ＭｎＧａ晶体室温条件下在［００１］方向， ６ ｈＯｅ外磁场已诱发产生 ０．３１％的输出应变，远超过巨磁致伸缩材料Ｔｅｒｆｅｎｏｌ－Ｄ输出应变０．１７％的水平．由于该晶体在磁场控制下表现出的大输出应变和应力，以及响应频率快和可精确控制的综合特性，使其可能在声纳、微位移器、线性马达、微波器件、振动和噪声控制、机器人和智能结构等诸多领域有重要应用，成为未来新一代驱动器和传感器材料．本文综述了Ｎｉ_２ＭｎＧａ单晶的基本性能、磁控形状记忆效应的机理、本质以及影响性能的因素等。

A New Kind of Functional Crystal Ni2MnGa

Ni2MnGa crystal is a new kind of functional material, which exhibits ferromagnetic, magnetostrictive, thermal and magnetically controlled shape memory properties. The nonstoichiometric Ni2MnGa crystal can show a strain of 0.31% along 001] direction in a magnetic field of 6kOe at room temperature; a 001]-directed stress of only 2MPa gives rise to a recoverable strain of 5%. As a kind of future actuator and sensor material, it will possibly be used in many fields, such as sonar, microactuator, linear motor, microwave device, vibration and noise control, robot and functional structure etc. This paper presents the properties of Ni2MnGa crystal, the essential and mechanism of the magnetic-induced martensitic transformation and magnetically controlled shape memory effect. Some factors which may influence the properties of Ni2MnGa are also discussed.