TEM studies of sintered Fe-Nd-B magnets

In sintered Fe-Nd-B magnets with additions of Al, Fe is substituted by Al in Fe14Nd2B but not in Fe4Nd1+&varepsilonB4. An additional phase containing Fe and Nd in nearly equal mass concentrations and enriched in Al was found in these magnets. Thin edges of Fe14Nd2B are found to decompose to mainly bcc α-Fe and hexagonal Nd2O3by selective oxidation in the TEM. Thin boundary layers of nm thickness are shown to consist of Nd-rich material of fcc structure with a ≃ 0.52 nm.