Effect of grain-boundary diffusion process on the geometry of the grain microstructure of Nd − Fe − B nanocrystalline magnets

摘要: Hot-deformed anisotropic $\mathrm{Nd}\ensuremath{-}\mathrm{Fe}\ensuremath{-}\mathrm{B}$ nanocrystalline magnets have been subjected to the grain-boundary diffusion process (GBDP) using a ${\mathrm{Pr}}_{70}{\mathrm{Cu}}_{30}$ eutectic alloy. The resulting grain microstructure, consisting of shape-anisotropic nanocrystals surrounded by $\mathrm{Pr}\ensuremath{-}\mathrm{Cu}$-rich intergranular phase, has investigated unpolarized small-angle neutron scattering and very scattering. data analyzed generalized Guinier-Porod model computing, independently, distance distribution function. We find that GBDP results in change geometry particles: In small-$q$ regime, from as-prepared sample exhibits slope about 2, which is characteristic for two-dimensional platelet-shaped objects, while manifests 1, signature one-dimensional elongated objects. evolution Porod exponent indicates smoothing surfaces due GBDP, accompanied an increase coercivity.