Microstructures and Magnetic Properties of Fe-Zr-B Based Nanocrystalline Alloys

We have studied the partitioning of B in Fe -14B and of Zr, B, Si, Cu and Au in FeZrB nanocrys-talline soft magnetic alloys by using atom probe field ion microscopy (APFIM) and high resolution electron microscopy (HREM) in atomic or nano-metric scales and'the effect of Si, Cu, andAuaddition on the magnetic properties. For Fe- 14B after annealing, a -Fe particles with diameters of about 50-100 nm formed and they contain high supersaturated B. For Fe - 7Zr-3B -1 Cu amorphous alloy, it was found that Cu atoms formed clusters prior to the crystallization reaction. During the crystallization, Cu-enriched clusters provided nucle-ation sites for a -Fe phase so that the nucleation density of a -Fe phase increased. For Fe - 7Zr -5B- 1Au amorphous alloys, Au clusters were observed during the nucleation and growth stage of primary a -Fe and a -Fe did not form at the sites of Au cluster. Hence Au does not enhance the nucleation density of a -Fe particles. For Fe-7Zr-4Si-2B alloys it was found that Si atoms are reje

Microstructures and Magnetic Properties of Fe-Zr-B Based Nanocrystalline Alloys

We have studied the partitioning of B in Fe -14B and of Zr, B, Si, Cu and Au in FeZrB nanocrys-talline soft magnetic alloys by using atom probe field ion microscopy (APFIM) and high resolution electron microscopy (HREM) in atomic or nano-metric scales and'the effect of Si, Cu, andAuaddition on the magnetic properties. For Fe- 14B after annealing, a -Fe particles with diameters of about 50-100 nm formed and they contain high supersaturated B. For Fe - 7Zr-3B -1 Cu amorphous alloy, it was found that Cu atoms formed clusters prior to the crystallization reaction. During the crystallization, Cu-enriched clusters provided nucle-ation sites for a -Fe phase so that the nucleation density of a -Fe phase increased. For Fe - 7Zr -5B- 1Au amorphous alloys, Au clusters were observed during the nucleation and growth stage of primary a -Fe and a -Fe did not form at the sites of Au cluster. Hence Au does not enhance the nucleation density of a -Fe particles. For Fe-7Zr-4Si-2B alloys it was found that Si atoms are rejected from a -Fe primary crystals and partitioned into the residual amorphous phase. This result suggests that Si addition does not cause reduction in inherent magnetostriction of a -Fe nano-particles, but it brings the volume fraction of the a -Fe particles to an optimum value so that the average magnetostriction of alloy becomes zero. This conclusion has been strengthened by comparing the changes in magnetostriction constants as a function of Si content in Fe-Zr-Si-B alloys.