Evidence for lattice softening of the Fe-Ga magnetostrictive alloy: Stress-induced local martensites

Publication date: 15 February 2018
Source:Materials & Design, Volume 140
Author(s): Xiaolian Liu, Meixun Li, Junming Gou, Qiaochu Li, Yunhao Lu, Tianyu Ma, Xiaobing Ren
The over tenfold magnetostriction enhancement by soluting nonmagnetic Ga into body centered cubic (BCC) Fe has been ascribed to crystal lattice softening, which indicates that the Fe-Ga solid solution lies in the crossover of martensitic transformation. Identifying the martensitic phase then becomes essential. Here we report the stress-induced local six-layer modulated monoclinic (6M) martensites in a Fe79Ga21 alloy solution-treated at 1373K. Although X-ray diffraction (XRD) and magnetic measurements reveal that the bulk sample exhibits BCC average structure, the transmission electronic microscopy (TEM) characterizations however show that the mechanically grinded foil sample contains local 6M phase. First principal calculations suggest that low formation energy barrier between the ordered D03 and the 6M phases are responsible for the stress-induced structural transformation. Our work provides evidence for the lattice softening of Fe-Ga solid solution, adding important insight into understanding the origin of its extraordinary magnetostriction enhancement.

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