Directional annealing studies on rapidly solidified Sm-Co-Nb-C alloys

In this paper, a process that develops texture in nanocrystalline permanent magnet alloys is presented. An originally isotropic material is passed through a high up-temperature gradient, inducing directional grain growth. Texture development by directional annealing of melt-spun Sm12Co88, (Sm12Co88)99Nb1, (Sm12Co88)99C1, and (Sm12Co88)98Nb1C1 alloys was examined. Samples directionally annealed were compared with conventionally annealed samples. Strong (0 0 6) in-plane texture was observed by X-ray diffraction in Sm12Co88 and (Sm12Co88)99Nb1 alloys and the anisotropy was corroborated by magnetic measurements (magnetic texture ∼20-53%). Directional annealing produced only slight texture in the (Sm12Co88)99C1 and (Sm12Co88)98Nb1C1 alloys. The development of texture is critically dependent on annealing temperature, the up-temperature gradient, translational velocity, and alloy composition. The activation energy for anisotropic grain growth was estimated to be ∼28 and ∼42 kJ mol−1 for Sm12Co88 and (Sm12Co88)99Nb1, respectively. These results indicate that directional annealing as a route to texture development in nanocrystalline permanent magnet alloys is a feasible process.