Structural and magnetic properties of nanocrystalline Fe-rich Fe-Nb-Nd-B sintered magnets produced by consolidating amorphous powders

Nanocrystalline bulk Fe/sub 88/Nb/sub 2/Nd/sub 5/B/sub 5/ and Fe/sub 86/Nb/sub 2/Nd/sub 7/B/sub 5/ alloys were made by consolidating amorphous powders with an electric-pulse-current sintering method and subsequent annealing. Bulk alloy made by consolidating amorphous powders has a higher density (the maximum density could reach 7.5 g/cm/sup 3/ consolidating at 873 K and 636 MPa) than that made by consolidating crystalline powders, presumably because the amorphous alloy softens around the crystallization temperature. The structure formed after annealing at 1023 K for 180 s shows a nanocrystalline composite consisting of bcc-Fe, Nd/sub 2/Fe/sub 14/B and Fe/sub 3/B or Fe/sub 2/B phases with grain sizes of 20-40 nm. The nanocrystalline bulk Fe/sub 88/Nb/sub 2/Nd/sub 5/B/sub 5/ alloy shows hard magnetic properties, remanence of 1.05 T, coercive force (H/sub cJ/) of 263 kA/m, maximum energy product ((BH)/sub max/) of 75 kJ/m/sup 3/.