Secondary recrystallization behavior in the rolled columnar-grained Fe-Ga alloys

The secondary recrystallization behavior with temperature increasing from 900 to 1080 °C was investigated in the rolled columnar-grained magnetostrictive Fe-Ga alloy sheets. The abnormal Goss grain growth occurred due to the inhibitory action of NbC in the Fe-Ga-0.1 at%NbC sheets. With the temperature increasing at a rate of 0.25 °C/min, the secondary recrystallization started below 950 °C. In addition to the S-induced surface energy effect, sulfur annealing also introduced a large number of S-rich and Nb-rich precipitates, which retarded the grain boundary migration on the surface. The abnormal grain growth was found to be restricted inside the sheet during the sulfur annealing process when the temperature was below 1000 °C, and a large amount of small island-like grains was remained on S-annealed sheets. After final Ar/H2 annealing processes, the S-rich precipitates and small island-like grains were eliminated, and sharp Goss orientation and high magnetostriction of 245 ppm were obtained in the final S-annealed sheets.