Partitioning behavior and the effect of Co on the Curie temperature of nanocomposite PrFeCoB hard magnetic alloys

The microstructure and phase chemistry of melt-spun nanocomposite Pr9.7Fe76.6Co7.8B5.9 and Pr9.2Fe69.4Co15.4B6.0 ribbons have been studied using three-dimensional atom probe (3DAP) and transmission electron microscopy. The microstructure of these alloys consists of two phases, bcc alpha -Fe-Co and tetragonal Pr-2(FeCo)(14)B. Practically all of the B and Pr atoms are rejected from the alpha -Fe-Co phase and are concentrated into the 2/14/1 hard magnetic phase. However, no significant difference of Co concentration between the two phases is observed. From the measured Co concentration in the 2/14/1 phase, it is explained why the effect of Co content on Curie temperature (T-c) is greater in the nanocomposite alloys than in single phase alloys. Predictions of T-c for the nanocomposite alloys based on the 3DAP composition data show excellent agreement with experimental measurements. (C) 2001 American Institute of Physics.