Ni54Fe19Ga27单晶的形状记忆和超弹性

本文研究了单晶Ni₅₄Fe₁₉Ga₂₇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],110],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× 10⁵ erg/cm³,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 in single crystal Ni54Fe19Ga27

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 crystallographic 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 = (1/2)M_sH_a =4.8× 10⁵ erg/cm³, 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.