Effect of Si/B ratio on magnetic properties and microstructure of FeSiBNbCuAl nanocrystalline alloys

The effect of Si/B ratio on the magnetic properties, microstructure, magnetic domain structure, and crystallization kinetics of Fe77Si10+xB9-xNb2Cu1Al1 (x=0, 1, 2 at%) nanocrystalline alloys has been investigated. The slight increase in Si/B ratio has minimal effect on the saturation magnetization of the alloys, but effectively increases the permeability and decreases the coercivity in a wide annealing temperature range. Substituting 2% Si for B significantly increases the activation energy of α-Fe(Si) growth and Fe3B precipitation, leading to the formation of uniform, fine and stable α-Fe(Si) grains. This structure is beneficial to reduce the magnetocrystalline anisotropy and magnetoelastic anisotropy of the alloy, and form wide and smooth-moving magnetic domains, thus significantly improving the soft magnetic properties.