High strength soft magnetic composites

There has been an increasing demand for high temperature soft magnetic materials with mechanical properties better than those of existing commercial materials such as FeCo alloys. We have designed new magnetic composites by reinforcing FeCo alloys with high strength tungsten fibers. The composite materials were fabricated by electrodeposition. In general, the as-deposited composites have a relatively high coercivity H_c and low magnetic permeability μ, because of induced strain during fabrication. After appropriate thermal annealing, the composites have good soft magnetic properties, comparable to commercial bulk alloys. However, the saturation induction is reduced due to the non-magnetic inclusions. The composites also show significant enhancements in yield strength and tensile strength that increases linearly with fiber volume fraction as seen in other common composite materials. In addition, near zero creep is observed at 600°C under a stress of 600 Mpa. The mechanical properties can be further improved by co-depositing soft magnetic material and Al₂O₃ onto the fibers. An approximately linear relationship was observed between the coercivity and volume fraction of Al₂O₃ particles. The square-root relationship was observed between the hardness and the Al₂O₃ concentration.