Ni_(54)Fe_(19)Ga-(27)单晶的形状记忆和超弹性

Shape memory effect and superelasticity in single crystal Ni_954)Fe_919)Ga_(27)

本文研究了单晶Ni_(54)Fe_(19)Ga_(27)不同方向的形状记忆效应、超弹性和磁性.研究发现,单晶样品具有良好的双向形状记忆效应.不同晶体学方向的相变应变随着热循环次数的变化而改变.在外应力作用下,通过应力诱发马氏体相变,样品在[001],[10],[111]方向分别产生了3.3%,2%和3%的可回复应变平台.磁性测量结果表明马氏体的磁晶各向异性能约为4.8×10~5erg/cm^3,远远小于变体孪生所需机械应力能,因此磁场的作用是使磁矩发生转动而不是使孪晶界移动,成功揭示了不能在NiFeGa中获得大磁感生应变的物理根源.

Shape memory effect and superelasticity are studied in this paper.At room temperature,perfect strain plateaus of 3.3%,2%and 3%are obtained in the[001],[110]and[111]directions.The energies required to induce the martensitic transformation in different crystal lographic directions are estimated from the stress-strain results.Each of the magnetization curves in the martensitic phase indicates that a magnetic anisotropy energy density K_u =1/2M_sH_a=4.8×10~5 erg/cm^3,which is far smaller than the mechanical driving force for variants twinning.This interpretes why only a little magnetic field induced strain in NiFeGa alloy has been observed so far.