Effect of boron additions on phase formation and magnetic properties of TbCu7-type melt spun SmFe ribbons

• A certain amount of boron additions can inhibit the emergence of the soft magnetic phase α-Fe and improve the ability of amorphous formation.
• There is a solubility limit of boron atom within melt spun Sm–Fe alloys with TbCu7-type structure, and the metastable phase Sm2Fe23B3 will appear when the content of boron exceeds the limit.
• The boron additions greatly refine the grain size of SmFe12B1.0ribbons at the surface velocity about 40 m/s, the mean grain size of about 22 nm.
• The following sequence of the hyperfine field H(6l)

Melt spun ribbons of a series of SmFe12Bx (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm–Fe–B melt spun ribbons with single phase TbCu7-type structure were prepared from the SmFe12Bx (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40 m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm–Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm–Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm2Fe23B3 that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu7-type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe12B1.0 melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36 kOe and a remanence of 4.8 kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe12 and SmFe12B1.0 ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)