On the nanostructural formation process in Fe-M-B (M=Zr or Nb) soft magnetic alloys

The nano-structural formation kinetics in soft magnetic Fe₉₀Zr₇B₃ and Fe₈₀Nb₆B₁₄ alloys have been investigated. The nanocrystallite formation in the Fe-Zr-B alloy is governed mostly by a nucleation-and-growth mechanism. On the other hand, the nano-structural formation mechanism in the Fe-Nb-B alloy shows a change in the fraction transformed range 0.1-0.2. The first- and second-stage nano-structural formation processes have been described by the nucleation-and-growth model with an Avrami exponent ∼1.5 and the grain-growth model with a grain-growth exponent of 1.5-3, respectively. This two-stage nature in the nano-structural formation kinetics can be attributed to a high population density of the primary bcc nuclei.