Nanostructured melt-spun Sm(Co, Fe, Zr, B)7.5 alloys for high-temperature magnets

High coercivity, the highest for Cu-free 2 : 17 Sm-Co ribbons, has been obtained in as-spun (H(c)=21.1 kOe) and short time annealed (H(c)=23.2 kOe) samples of Sm(Co/bal/Fe/z/Zr/y/B(x))/7.5/ alloys, with varying B, Zr, and Fe content (x = 0-0.06, y=0-0.16, z = 0.08-0.3) and wheel speed. In as-spun samples, the TbCu(7) type structure and in annealed samples the Th(2)Zn/17/ and CaCu(5) type structures is observed, plus fcc Co as minority phase is observed. Reduced remanence (M/r//M/s/) is higher than 0.7. High-temperature magnetic measurements show very good stability above 300 deg C with coercive field as high as 5.2 kOe at 330 deg C. For annealed Sm(Co/bal/Fe/0.3/Zr/0.02/B/0.04/)/7.5/, very good loop squareness and high maximum energy product of 10.7 MGOe have been obtained. Increasing Zr content results in less uniform microstructure of annealed ribbons.