Structural and microstructural evolution of nanocrystalline soft magnetic Fe_93-x-yZr₇B_XCu_y alloys

The effects of boron and copper on the evolution of structure and microstructure were examined in Fe_93-x-yZr₇B _xCu_y (x =3 and 9 at. %; y =0 and 1 at. %) alloys upon crystallization. B and Cu have opposite influence on the stabilization of the amorphous phase. Increasing B content leads to the formation of compounds rich in Fe and Zr depending upon Cu content. Cu plays a significant role in refining the microstructure. In Cu-free high B alloy, the grain growth of Fe crystallites was observed. This is attributed to the formation of Fe-Zr based compounds, which consumes Zr atoms. In Cu-containing high B alloy, due to the absence of such a reaction, Zr atoms are effective in pinning the bcc Fe grain boundaries giving rise to the nanocrystalline microstructure. NanoEDXS studies show the enrichment of Zr at bcc Fe grain boundaries confirming the proposed grain refinement process.