Effects of Precipitate Element Addition on Microstructure and Magnetic Properties in Magnetostrictive Fe83Ga17alloy

Abstract

The <100> oriented <TEX>$Fe_{83}Ga_{17}$</TEX> alloys with various contents of NbC or B were prepared by directionally solidification method at the growth rate of <TEX>$720mm{\cdot}h^{-1}$</TEX>. With a small amount of precipitates, the columnar grains grew with cellular mode during directional solidification process, while like-dendrite mode of grains growth was observed in the alloys with higher contents of 0.5 at% due to the dragging effect of precipitates on the boundaries. The NbC precipitates disperse both inside grains and along the boundaries of <TEX>$Fe_{83}Ga_{17}$</TEX> alloys with NbC addition, and the Fe2B secondary phase particles preferentially distribute along the grain boundaries in B-doped alloys. Precipitates could affect grain growth and improved the <100> orientation during directional solidification process. Small amount of precipitate element addition slightly increased the magnetostrictive strain, and a high value of 335 ppm under pre-stress of 15 MPa was achieved in the alloys with 0.1 at% NbC. Despite the fact that the effect on magnetic induction density of small amount of precipitates could be negligible, the coercivity markedly increased with addition of precipitate element for <TEX>$Fe_{83}Ga_{17}$</TEX> alloy due to the retarded domain motion resulted by precipitates.