Sampling the Cu-Fe-Co phase diagram by severe plastic deformation for enhanced soft magnetic properties

TL;DR

This study explores how severe plastic deformation via high-pressure torsion can produce nanocrystalline and supersaturated solid solutions in Cu-Fe-Co alloys, enhancing their soft magnetic properties and microstructure stability.

Contribution

It demonstrates a novel method to synthesize stable, nanocrystalline soft magnetic Cu-Fe-Co materials with tailored microstructures using high-pressure torsion.

Findings

Single-phase supersaturated solid solutions achieved at room temperature.

Nanocrystalline microstructures formed at higher ferromagnetic contents.

Enhanced magnetic moments observed in nanocomposite microstructures.

Abstract

Initial powder mixtures of Cu, Fe and Co are exposed to severe plastic deformation by high-pressure torsion to prepare solid solutions. A broad range of compositions is investigated, whereas this study aims at the synthesis of soft magnetic materials and therefore at the formation of a homogeneous and nanocrystalline microstructure. For intermediate ferromagnetic contents, high-pressure torsion at room temperature yields single-phase supersaturated solid solutions. For higher ferromagnetic contents, two consecutive steps of high-pressure torsion deformation at different temperatures yield the desired nanocrystalline microstructure. Depending on the Co-to-Fe-ratio, either a single-phase supersaturated solid solution or a nanocomposite forms. The composite exhibits an enhanced magnetic moment, indicating the formation of a (Fe,Co)-alloy upon severe plastic deformation. Soft magnetic properties are verified for large Co-to-Fe-ratios and this microstructure is found to remain stable up to 400 {\deg}C.