Multi-step crystallization evolution in nanocomposite Pr8Fe86B6alloys

A multi-step crystallization evolution has been observed in melt-spun nanocomposite Pr 8 Fe 86 B 6 alloys, resulting in drastically different magnetic properties. The ribbons spun at different wheel speeds consist of different volume fraction of an amorphous structure. Upon annealing the partially amorphous ribbons, a single transformation directly into Pr 2 Fe 14 B phase has been detected since the pre-existed 2 : 14 : 1 nanocrystallites serve as nucleation centres. However, a multiple-stage structural evolution was observed in the fully amorphous ribbons that crystallize first into metastable TbCu 7 -type phase and then Pr 2 Fe 23 B 3 phase before they finally transform into a mixture of Pr 2 Fe 14 B and α-Fe. The microstructure in the samples with partially amorphous precursors is much homogeneous and finer with the grain size around 10–30 nm.