Influence of Fe, Zr, and Cu on the microstructure and crystallographic texture of melt-spun 2:17 Sm–Co ribbons

Abstract

A comprehensive study on melt-spun 2:17 Sm–Co ribbons prepared at low wheel speed was undertaken in order to understand the effects of composition on the microstructure and formation of crystallographic texture. A high degree of texture was observed in melt-spun SmCo8.5 and Sm(Co0.9Fe0.1)8.5 ribbons prepared at 5 m/s with easy magnetization axis being parallel to the longitudinal direction of the ribbons. However, Zr was found to reduce the crystallographic texture and the Sm(Co0.74Fe0.1Zr0.04Cu0.12)z ribbon is isotropic. Scanning electron microscopy (SEM) observation showed that the formation of texture is attributed to a regular dendritic structure, with their long axis parallel to the longitudinal direction of the ribbons. The size and alignment of dendritic grains are significantly modified by Zr and Cu substitution for Co and the Sm(Co0.74Fe0.1Zr0.04Cu0.12)z ribbons are composed of many small areas with different alignments of the dendrites. X-ray diffraction patterns of crushed isotropic (d⩽20 μm) ribbons of Sm(Co0.74Fe0.1Zr0.04Cu0.12)8.5 show very high degree of texture and thus these ribbons have potential applications in preparing anisotropic bonded magnets. After an appropriate annealing, a coercivity of over 2.5 T has been obtained in Sm(Co0.74Fe0.1Cu0.12Zr0.04)z ribbons with z=7.5 and 8.0, and the coercivity mechanism is typical of the domain-wall pinning. This is consistent with transmission electron microscopy observation, which reveals a cellular and lamellar structure in the as-annealed ribbons.