Ferromagnetic shape memory in the NiMnGa system
Ferromagnetic shape memory in the NiMnGa system
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DOI：
10.1109/20.799080
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发表时间：
1999-09-01
影响因子：
2.1
通讯作者：
Kokorin, VV
中科院分区：
文献类型：
--
作者：
Tickle, R;James, RD;Kokorin, VV
应变与场的测量的铁磁形状记忆合金在NiMnGa系统证明了最大的磁致伸缩应变到目前为止，近1.3%。这些应变是通过场致变体重排在马氏体状态下实现的。描述了一种实验装置，该装置提供双轴磁场和单轴压缩预应力，并具有温度控制，同时用光学显微镜记录微观结构变化。发现磁致伸缩响应对应力偏置马氏体变体结构引起的初始状态敏感，并且表现出与孪晶边界迁移率相关的速率效应。恒定应力下的实验结果表明，工作输出能力，实验结果进行了解释，使用的理论基础上最小化的微磁能功能，包括施加的磁场，应力和退磁能量，它被发现，该理论提供了一个很好的定性描述材料的行为，但显着高估产生的应变量。关于马氏体的磁各向异性和变体形核的问题进行了讨论，关于这种差异。
Strain versus field measurements for a ferromagnetic shape memory alloy in the NiMnGa system demonstrate the largest magnetostrictive strains to date of nearly 1.3%. These strains are achieved in the martensitic state through field-induced variant rearrangement, An experimental apparatus is described that provides biaxial magnetic fields and uniaxial compressive prestress with temperature control while recording microstructural changes with optical microscopy, The magnetostrictive response is found to be sensitive to the initial state induced by stress-biasing the martensitic variant structure, and exhibits rate effects related to twin boundary mobility. Experiments performed with constant stress demonstrate work output capacity, Experimental results are interpreted by using a theory based on minimization of a micromagnetic energy functional that includes applied field, stress, and demagnetization energies, It is found that the theory provides a good qualitative description of material behavior, but significantly overpredicts the amount of strain produced. Issues concerning the martensitic magnetic anisotropy and variant nucleation are discussed with regard to this discrepancy.