Magnetic hardening of Ce2Fe14B

We report an effort to optimize the room-temperature permanent magnet properties of Ce-Fe-B materials rapidly solidified by melt spinning. Starting alloy compositions in the ternary phase diagram were selected systematically. Ribbons were melt spun from them at a quench wheel velocity of 35 m/s, corresponding to a solidification rate high enough to yield mostly amorphous or nanocrystalline material. Heat treatment above 450 °C crystallizes Ce2Fe14B, as x-ray diffraction clearly indicates, with the concomitant development of hard magnetic properties. The anneal temperature yielding optimum remanence Br, intrinsic coercivity Hci, and energy product (BH)max was determined in each case. For the ingot composition Ce17Fe78B6, we obtain Br = 4.9 kG, Hci = 6.2 kOe, and energy product (BH)max = 4.1 MGOe in ribbons comprised principally of Ce2Fe14B. This composition differs substantially from the optimum Nd13Fe82B5 stoichiometry for melt-spun magnets based on Nd2Fe14B and can be understood from a comparison of the distinct Ce-Fe-B and Nd-Fe-B phase diagrams.