Microstructure related disparity of the magnetostriction in the oriented directionally solidified Fe81Ga19 polycrystals

Abstract

Although lots of previous researches have proved that directional solidification was an effective technique to prepare the <100> oriented Fe81Ga19 polycrystals, there still existed disparity of the magnetostriction in these oriented samples. It greatly affects the production and application of Galfenol. Here, we find that the difference in magnetostriction is originated from phase constitution. The low-magnetostriction Fe81Ga19 polycrystals have more D03 phase and a small amount of the modified-D03 phase, whereas the high-magnetostriction polycrystals possess a higher volume fraction of the modified-D03 phase. Coincident magnetostriction can be obtained after a further annealing process, which is helpful to retain the A2 matrix to the greatest extent, suppress the D03 phase and facilitate the formation of the modified-D03 phase. Our work provides a guidance to produce <100> oriented Fe81Ga19 polycrystals with stable magnetostrictive performances.