Influence Of Longitudinal Magnetic Field Annealing On The Soft Magnetic Properties For The FeCo-based Dual-phase Nanocrystalline Alloys

The microstructure and the soft magnetic properties of(Fe1-xCox)78.4Si9B9Nb2.6Cu1(x=0.35,0.5,0.65,1)、(Fe0.5Co0.5)73.5Nb3-xVxSi13.5B9Cu（x=0,1）、Fe39.4-xCo40Nb2.6Si13.5B9Cux(x=0.5,1,1.5) alloys were investigated. Theinfluence of longitudinal magnetic field annealing on the crystalline volume fractionVcry, saturation magnetostriction λs, effective magnetic anisotropy <K> together withtemperature dependence of initial permeability (μi~T curves) for the dual-phasenanocrystalline alloys were mainly discussed.X-ray diffraction (XRD) showed that the dual-phase nanocrystalline structurewith bcc α-FeCo and residual amorphous phase was formed in the studied alloys aftervacuum annealing at proper temperatures, the crystal phase volume fraction and thegrain size changed with the alloy composition, annealing temperature and ways ofannealing. According to the μi~T of curves for as-quenched alloys, the Curietemperature of amorphous alloys was detected, which offered the basis of magneticannealing temperature.The experimental results showed that the magnetic annealing can enhance theVcryand significantly reduce the λs. The λSof nanocrystalline alloys decreased tovarying degrees, which is due to the rearrangement of magnetic atoms along theapplied field. However, the <K> of nanocrystalline alloys increased because of theinduced a uniaxial anisotropy. The nanocrystalline alloys were further crystallizationafter magnetic field annealing at proper temperatures, which results in theenhancement of Vcry. In addition, the content of Co, V and Cu elements has anobvious effect on the λsand <K> for the FeCo-based alloys.Saturation magnetostriction λSand effective anisotropy <K>, were the two keyfactors which were corretated with initial permeability μi. The rduced λscan improvethe soft magnetic properties and the enhanced Vcrycan improve the high-temperaturesoft magnetic properties. Experiments showed that after magnetic annealing at propertemperatures, the room-and high-temperature initial permeability of the FeCo-basednanocrystalline alloys were improved.