Magnetostriction and surface-energy-induced selective grain growth in rolled Galfenol doped with sulfur

The surface-energy-induced selective grain growth with a specific surface plane can be governed in polycrystalline (Fe_81.3Ga_18.7) + 0.5at.%B alloys doped with sulfur by controlling the segregation of sulfur through conventional rolling and texture annealing, where boron improves ductility due to suppressing grain boundary fracture during rolling process. The textured sheet, which was annealed at 1200°C for 2h under flowing argon and then quenched in water, exhibits a maximum magnetostriction of about 200 ppm along the rolling direction. During an argon annealing process, a convex profile in magnetostriction as a function of annealing time is formed. As the annealing temperature increases, the observed peak in the convex profiles shifts to less annealing time and also narrows. As-rolled (Fe_81.3Ga_18.7) + 0.5 at.%B + 0.005 at.%S sheets with large amounts of sub-grain which most likely have been deformed by the rolling process have some {100} and {111} grains parallel to the rolling direction. While texture annealing appears to eliminate the majority of the sub-grains present to below 1% of sub-structured or deformed area in the sheet annealed at 1200°C for 2h. From a texture standpoint the some clustered {100} poles were found and ~25° away from the rolling direction. And the {100} poles are centered right on the rolling direction for the highly textured subset.