EFFECT OF NB ADDITION ON THE CRYSTALLIZATION BEHAVIOR AND MAGNETIC-PROPERTIES OF MELT-SPUN FE-RICH FE-ND-B RIBBONS

We compared the crystallization behavior and subsequent magnetic prope rties of alpha-Fe/Nd2Fe14B-based exchange-spring magnets with and with out Nb addition, using differential thermal analysis, X-ray diffractio n, transmission electron microscopy, and vibrating sample magnetometer , In the optimally annealed Nd4Fe90Nb2B4 alloy, uniformly distributed alpha-Fe grains 50-80 nm in diameter are surrounded by Nd2Fe14B1 grain s 10-20 nm in diameter as well as by amorphous intergranular layer reg ions enriched with Nb. The remanence, the coercivity, and the energy p roduct are 1.35 T, 210 kA m(-1) (2.65 kOe) and 103 kJ m(2), respective ly, In the annealed alloy without Nb, the alpha-Fe and Nd2Fe14B1 phase s are brought about from two different intermediate states, resulting in a heterogeneous distribution. (C) 1998 Elsevier Science S.A.