The role of boron in nanocrystalline FeZrB soft magnetic alloys

The microstructure and soft magnetic properties of crystallization-induced alloys in FeZr and FeZrB systems were investigated. Melt-spun amorphous Fe₉₂Zr₈ and Fe₉₁Zr₇B₂ alloys were found to crystallize through two distinct stages; the first and second stage are due to primary crystallization of a nanocrystalline b.c.c. phase and crystallization of a residual solute-enriched amorphous phase into Fe₃Zr and Fe₂Zr respectively. The addition of B into amorphous FeZr alloys causes the refinement of the primary b.c.c. crystals, resulting in a significant improvement of the soft magnetic properties of the annealing-induced alloys. Grain coarsening of the nanocrystalline b.c.c. phase as well as the formation of compounds is suppressed by the addition of B. This is presumably of a significant increase in the crystallization temperature of the residual amorphous phase resulting from the combined redistribution of Zr and B elements between the primary and parent amorphous phases.