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

Rapid Secondary Recrystallization of the Goss Texture in Fe81Ga19 Sheets Using Nanosized NbC Particles

“…When the temperature approached 950 °C, a large magnetostriction coefficient of 295 ± 9 ppm was obtained in the Fe 81 Ga 19 sheets, corresponding to sharp Goss orientation. This magnetostriction coefficient was higher than those reported for Fe–Ga alloys after secondary recrystallization by inhibitors and in a special atmosphere [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”

“…Figure 9 summarizes the final annealing temperatures and magnetostriction coefficients of the Fe–Ga thin sheets as reported in the literature [ 7 , 11 , 12 , 13 , 14 , 16 , 17 , 25 , 26 , 27 , 28 ]. The magnetostriction coefficient of the Fe 81 Ga 19 sheet secondarily recrystallization annealed in an N 2 atmosphere in this study was equivalent to the values obtained in the cases of using microsized NbC particles and using the surface-energy effect of H 2 S; it was higher than the values obtained using nanosized sulfides in a N 2 + H 2 atmosphere, or using microsized NbC in Ar + S or H 2 atmosphere; it was much higher than the values obtained for microsized Fe 2 B or NbC.…”

“…A large number of microsized NbC particles act as a strong inhibitor for the Fe–Ga thin sheet, but the surface energy effect of H 2 S is the main driving force for secondary recrystallization at high temperatures ranging from 1200 to 1300 °C, because the texture formed in primary recrystallization contributes little to the AGG of the Goss texture [ 18 , 32 ]. The nanosized NbC particles rapidly coarsen at temperatures of 900–950 °C, resulting in a rapid decrease in the pinning force; the advantage of the large grain size of the special initial columnar crystals is also required for complete recrystallization [ 13 , 14 ]. Nanosized sulfides with a size of 30–50 nm provide a strong pinning force for inhibiting the growth of matrix grains; however, the pinning force is too strong at low annealing temperatures, owing to the initial small size and low ripening rate; therefore, a higher annealing temperature is required for complete recrystallization [ 17 ].…”

“…Na et al reported that Goss grains with an area fraction of ~98% were obtained in rolled Fe–Ga sheets with a magnetostriction coefficient of 245–292 ppm using 1.0 mol% microsized NbC particles (1–5 µm) to inhibit the growth of matrix grains and annealing under an Ar and H 2 S atmosphere [ 11 , 12 ]. Yuan et al [ 13 , 14 ] reported that strong Goss texture with a magnetostriction coefficient of 245 ppm was obtained in rolled columnar-grained Fe 83 Ga 17 alloys by using 0.1 mol% microsized NbC particles, and the surface segregation of S was imperative for retarding the growth of surface grains as the annealing temperature rose to 1200 °C. Liu et al [ 15 , 16 ] reported that the AGG of Goss grains was induced by nanosized NbC precipitate particles in rolled sharp <100>-oriented columnar-grained Fe 82 Ga 4.5 Al 13.5 after annealing at 1085 °C.…”

“…Precipitates sized 30–100 nm can impose a strong inhibiting force on the primary grains, and the inhibiting force is clearly lower when the size is beyond this range. However, complete secondary recrystallization cannot be induced only by 0.1 mol% nanosized NbC precipitates in an Fe–Ga thin sheet; strong Goss texture with size advantage in primary recrystallization realized by initial directional solidification is necessary [ 13 , 14 ]. The sulfide precipitates sized 30–50 nm require a higher temperature and longer time to coarsen, and provide the driving force necessary for the AGG of Goss grains [ 17 ].…”