Formation and crystallization behavior of Fe-based amorphous precursors with pre-existing α-Fe nanoparticles-Structure and magnetic properties of high-Cu-content Fe-Si-B-Cu-Nb nanocrystalline alloys

Structure, crystallization behavior, and magnetic properties of as-quenched and annealed Fe81.3Si4B13Cu1.7 (Cu1 .7) alloy ribbons and effects of Nb alloying have been studied. Three-dimensional atom probe and transmission electron microscopy analyses reveal that high-number-density Cu-clusters and Pre-existing Nano-sized alpha-Fe Particles (AN-alpha-Fe) are coexistence in the melt-spun Cu-1.7 amorphous matrix, and the PN-alpha-Fe form by manners of one-direction adjoining and enveloping the Cu-clusters. Two-step crystallization behavior associated with growth of the PN-alpha-Fe and subsequent nucleation and growth of newly-formed alpha-Fe is found in the primary crystallization stage of the Cu(1.7 )alloy. The number densities of the Cu-clusters and PN-alpha-Fe in melt-spun Fe81.3-xSi4B13Cu1.7Nbx alloys are gradually reduced with enriching of Nb, and a fully amorphous structure forms at 4 at.% Nb, although smaller Cu-clusters still exist. After annealing, 2 at.% Nb coarsens the average size (alpha-Fe ) of the alpha-Fe grains from 14.0 nm of the Nb-free alloy to 21.6 nm, and 4 at.% Nb refines the alpha-Fe to 8.9 nm. The mechanisms of the alpha-Fe nucleation and growth during quenching and annealing for the alloys with large quantities of PN-alpha-Fe as well as after Nb alloying have been discussed, and an annealing-induced alpha-Fe growth mechanism in term of the barrier co-contributed by competitive growth among the PN-alpha-Fe and diffusion-suppression effect of Nb atoms has been proposed. A coercivity (H-c) proportional to D-proportional to-Fe(3) correlation has been found for the nanocrystalline alloys, and the permeability is inverse with the H-c. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The structure, crystallization behavior, and magnetic properties of Fe81.3Si4B13Cu1.7 alloy ribbons were studied, as well as the effects of Nb alloying. High-density Cu-clusters and Pre-existing Nano-sized alpha-Fe Particles were found in the amorphous matrix, and the number densities of these clusters were gradually reduced with Nb enrichment. Nb alloying also affected the average size of alpha-Fe grains after annealing, with 4 at.% Nb refining the grains to 8.9 nm. Mechanisms of alpha-Fe nucleation and growth during quenching and annealing were discussed, and a coercivity correlation with alpha-Fe was found, with permeability inversely related to coercivity.