2001 Volume 42 Issue 10 Pages 2102-2111
The isothermal crystallisation processes and the decomposition behaviours of the crystallised phases in Pr4.5Fe77B18.5 amorphous ribbons prepared by a melt quench technique have been investigated by means of differential thermal analysis, X-ray diffraction, and high resolution transmission electron microscopy, and the following results were obtained. The phase initially crystallised is Fe3B and the crystallisation of Pr2Fe23B3 particles occurs immediately after the Fe3B formation. This is probably due to the fact that Fe3B/amorphous interphase boundaries provide potent nucleation sites for Pr2Fe23B3 particles in view of chemistry in the vicinity of Fe3B particles and the structure of the interfaces. Then, fine hard magnetic Pr2Fe14B particles nucleate at Fe3B interfaces directly. In the following processes, Pr2Fe14B and Pr2Fe23B3 particles grow by the coalescence of fine particles. In the later annealing stages, Pr2Fe23B3 particles decompose into Pr2Fe14B networks involving spherical α-Fe particles in a eutectoid-like mode. At the final stage of annealing these Pr2Fe14B networks transform in-situ into those of PrFe4B4.