Surface-energy-induced selective growth of (001) grains in magnetostrictive ternary Fe–Ga-based alloys

Abstract

Surface-energy-induced selective grain growth has been used to increase the presence of preferred planes in polycrystalline ternary Fe–Ga based alloys and thereby maximize the magnetostrictive performance of these alloys. In this study, alloys were either doped with elemental sulfur or annealed under sulfur atmospheres to control the sulfur concentration on the surface of samples during annealing. We show that the segregation of sulfur, which is known to play an important role in controlling surface energy, can be correlated to the selective growth of {001} grains and an increase in the saturation magnetostriction of the samples. The results show that sulfur atoms are adsorbed (diffused) from the sulfur atmosphere (bulk interior) and segregate on the sample surface. The correlation between surface chemistry, texture development and magnetostriction is presented. The formation of {001} grains occurred under slight surface segregation of sulfur, i.e. at levels of concentration of surface sulfur between 0.5 and 1.35 at.%, for alloys of (Fe0.813Ga0.187)99B1 and (Fe0.813Ga0.187)99.5B0.5 doped with 50 ppm S. In the case of (Fe0.81Ga0.19)99(NbC)1 alloy annealed under a H2S atmosphere, abnormal growth of (001) grains resulted in 88.3% of the sample area being covered with a (001) grain.

Magnetostriction of the polycrystalline Fe80Al20 alloy doped with boron

“…In Fe-Ga, methods 1 and 3 have already been proven to be very effective for improving the linear magnetostriction of this alloy [11][12][13]. A highly oriented crystal has been shown to present a value of 3/2 k 100 = 350 ppm, and quenched samples have higher magnetostriction than slow cooled samples [14].…”

Effect of Initial Oriented Columnar Grains on the Texture Evolution and Magnetostriction in Fe–Ga Rolled Sheets

“…After the primary annealing, samples were rapidly heated from 850 to 900 • C at a rate of 10 • C/min in the furnace, and they were then slowly heated from 900 to 1080 • C at a controlled rate of 0.25 • C/min, and they were finally cooled by air to room temperature without dwell at 1080 • C. as the most effective way to achieve the sharp <001> orientation along the rolling direction in the rolled Fe-Ga alloy sheets [13][14][15][16][17][18]. Previous studies have reported the achievement of sharp Goss orientation, by the combined effects of NbC particles as inhibitors and sulfur-induced surface energy [15][16][17]. Presently, most studies are about the rolling and recrystallization behaviors of the Fe-Ga polycrystalline alloys with equiaxed grains, and mainly focus on the influence of the final annealing process on abnormal grain growth.…”

“…In order to produce thin sheets with reasonable robustness and magnetostrictive properties, efforts have been made to produce the textured sheets by rolling and secondary crystallization processes [8][9][10][11][12]. Up to now, the secondary recrystallization, also named abnormal grain growth (AGG), of Goss-oriented ({110}<001>) grains has been considered as the most effective way to achieve the sharp <001> orientation along the rolling direction in the rolled Fe-Ga alloy sheets [13][14][15][16][17][18]. Previous studies have reported the achievement of sharp Goss orientation, by the combined effects of NbC particles as inhibitors and sulfur-induced surface energy [15][16][17].…”

Selective Abnormal Growth Behavior of Goss Grains in Magnetostrictive Fe-Ga Alloy Sheets

“…Thermal mechanical processes involving deformation and recrystallization have been employed to produce rolled Fe-Ga sheets [8][9][10][11][12] , and <001> orientation along the rolling direction (RD) is preferred to maximize the magnetostrictive performance. Up to now, the secondary recrystallization, also named by abnormal grain growth (AGG), of Goss oriented ({110}<001>) grains has been the most effective way to achieve the sharp <001> orientation and large magnetostriction along the RD in the rolled Fe-Ga sheets [13][14][15][16][17][18] . Previous studies have reported the achievement of sharp Goss orientation, by the combined effects of NbC particles as inhibitors and sulfur-induced surface energy effects [15][16][17] .…”

“…Up to now, the secondary recrystallization, also named by abnormal grain growth (AGG), of Goss oriented ({110}<001>) grains has been the most effective way to achieve the sharp <001> orientation and large magnetostriction along the RD in the rolled Fe-Ga sheets [13][14][15][16][17][18] . Previous studies have reported the achievement of sharp Goss orientation, by the combined effects of NbC particles as inhibitors and sulfur-induced surface energy effects [15][16][17] . However, most of studies focused on the in uence of nal annealing time and temperature, and annealing processes at temperatures above 1373 K for a special time were employed to produce the AGG.…”