Soft magnetic properties and microstructure of Fe84−xNb2B14Cux nanocrystalline alloys

•New Fe84−xNb2B14Cux nanocrystalline alloys are successfully synthesized.•Appropriate Cu addition avoids crystallization during quenching in this alloy system.•The Fe83Nb2B14Cu1 nanocrystalline alloy exhibits excellent soft magnetic properties.•The alloy system has a large economical advantage and convenient productivity.

Magnetic properties and microstructure of new Fe84−xNb2B14Cux nanocrystalline alloys were investigated. We found that the microstructure was refined and soft magnetic properties of this alloy system were enhanced with proper Cu addition and annealing conditions. It was also discovered that the mean grain size firstly increases, then decreases to a minimum, and finally increases again with increasing annealing temperature for Fe83Nb2B14Cu1 nanocrystalline alloy, and this phenomenon was interpreted by the grain growth mechanism. Moreover, after annealing at 813 K for 180 s, Fe83Nb2B14Cu1 nanocrystalline alloy shows a fine microstructure with mean grain size of 16 nm, and exhibits excellent soft magnetic properties, such as high saturation magnetic flux density (1.7 T), low coercivity (7 A/m) and high permeability (2.8 × 104). The result indicates that this alloy should have a promising application in the soft magnetic industry.