Investigation on high-temperature magnetic permeability of Si-rich nanocrystalline (Fe0.9Co0.1)74.5Nb2Si17.5B5Cu1 alloy

Abstract

The temperature dependence of initial permeability (μi-T curve) for as-quenched and annealed Si-rich (Fe0.9Co0.1)74.5Nb2Si17.5B5Cu1 alloy was investigated. The results showed that fewer Co doping into Fe74.5Cu1Nb2Si17.5B5 can reduce the onset primary crystallization temperature Tx1, enhance the Curie temperature of amorphous phase Tcam, and improve the high-temperature soft magnetic properties. After annealing at 480–650 °C, the common feature of μi-T curve is that the μi increases with T from room temperature and reaches a peak value at a certain temperature, which depends on the annealing temperature Ta, then μi decreases with T. This kind of μi-T curves is different from that of the common Co-contained Finemet-type alloys ever reported. The optimal high-temperature magnetic softness was obtained by annealing at 540 °C, the higher μi of 6500 at 10 kHz can be kept up to 500 °C. Such a magnetic softness at elevated temperature is superior to that of Fe74.5Nb2Si17.5B5Cu1 alloy and other Co-contained Finemet-type nanocrystalline alloys with higher Co content.