Hot-pressed Sm2Fe17Nx/Fe-Co composites:: Factors controlling densification and in situ nitrogenization of Sm2Fe17 phase

The effects of powder preparation and conditions of hot pressing on the structure and density of consolidated Sm(2)Fe(17)N(x) and Sm(2)Fe(17)N(x)/Fe-Co magnets have been studied. Densities achieved in the case of Sm(2)Fe(17)N(x) powders prepared through a low-energy milling were higher than after a high-energy milling. The difference is mostly caused by the different particle size, and it can be eliminated by an additional low-energy milling of the coarse high-energy milled powder. The presence of a ductile soft magnetic phase greatly facilitates densification, leading to considerably higher absolute and relative densities in hot-pressed Sm(2)Fe(17)N(x)/Fe(0.65)Co(0.35) composites. We have found that during hot pressing, nitrogenization of the Sm(2)Fe(17) phase may occur in situ if pressed together with Fe-Co-N powders. Because Fe-Co-N releases nitrogen below the decomposition temperature of Sm(2)Fe(17)N(x), we were able to fabricate the Sm(2)Fe(17)N(x)/Fe(0.65)Co(0.35) composite with the density up to 7.6 g/cm(3) by hot-pressing mixtures of Sm(2)Fe(17) and (Fe(0.65)Co(0.35))(89)N(11) powders. (C) 2008 American Institute of Physics.