【作者】 何宝明；

【导师】 王省哲；

【作者基本信息】 兰州大学 ， 工程力学， 2008， 硕士

【摘要】 铁磁形状记忆合金（Ferromagnetic Shape Memory Alloy,简称FSMA）是一种新型功能材料,具有强铁磁性,大磁诱发应变,温控和磁控形状记忆效应,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等很多优点,在执行器领域有广泛的应用前景。本文对铁磁形状记忆合金Ni₂MnGa在外加磁场和应力作用下的力-磁耦合行为进行了较系统的实验研究。首先,对文献中所涉及的铁磁形状记忆合金Ni₂MnGa单晶磁诱发应变产生的微观机制和行为进行了较为系统的论述。Ni₂MnGa合金具有伪弹性行为,在磁场较低时（1＜H＜3 kOe）,表现出局部伪弹性行为;Ni₂MnGa单晶由于具有择优取向的马氏体变体,在外磁场作用下能够产生大的磁诱发应变,力—磁耦合作用较强。其次,笔者利用自行设计的实验装置对外加磁场、应力场共同作用下的铁磁形状记忆合金Ni₂MnGa多晶的磁-力学特性进行了实验测试与研究,分别获得了两种组分Ni₅₂Mn₂₇Ga₂₁和Ni₅₄Mn₂₅Ga₂₁多晶样品在不同磁场倾角、不同预加应力下的磁化曲线和磁滞回线;以及不同外加磁场及磁场倾角下的应力-应变曲线和磁致应变曲线等磁-力学特性曲线。结果表明铁磁形状记忆合金多晶沿样品轴向所测的饱和磁化强度随磁场倾角的增大而减小,施加预应力并不显著影响样品的磁化曲线和磁滞回线;各种角度时不同磁场对两种多晶样品的应力-应变关系影响均很小;Ni₂MnGa多晶力—磁耦合作用较弱。更多还原

【Abstract】 Ferromagnetic shape memory alloys（FSMAs）are a new type of functional material,which exhibit many outstanding advantages such as high ferromagnetism, large magnetostrain,thermoelastic and magnetic shape memory effect.Ferromagnetic shape memory alloys are potential in actuators application because its response frequency is as high as piezoelectric materials,strain-stress output can be compared with thermal shape memory alloys.In this paper,experiment on magneto-mechanical coupling behavior of Ni₂MnGa under magnetic field and stress are systemically studied.Firstly,the micro-mechanism and behavior of magnetostrain of single crystal Ni₂MnGa ferromagnetic shape memory alloys has been expatiated based on references.Ni₂MnGa exhibits pseudoelastic behavior,when the material is applied at low magnetic field（1＜H＜3 kOe）,the pseudoelastic behavior is partial.Ni₂MnGa single crystal,because of highly-preferred twin variants,can produce huge magnetostrain under magnetic field,magneto-mechanical coupling is strong.Secondly,the effects of applied axial pre-compressive stresses and magnetic fields on the magneto-mechanical characteristics of ferromagnetic shape memory alloys Ni₅₂Mn₂₇Ga₂₁and Ni₅₄Mn₂₅Ga₂₁polycrystalline samples have been studied experimentally with self-designed equipment.The magnetization curves and magnetization hysteresis loops measured along axial direction of the two kinds of samples with different inclination angles of applied magnetic fields and axial pre-compressive stresses were obtained,as well as stress-strain loops and magnetostrain curves.The experimental results showed that the saturation magnetization values measured along axial direction of the samples decrease with the inclination angle of applied magnetic fields increases.The pre-compressive stresses have no obvious effect on the magnetization curve and magnetization hysteresis loop. The applied magnetic fields with different inclination angles show little effect on the stress-strain loop.Magneto-mechanical coupling of Ni₂MnGa Polycrystals is weak.更多还原