Effect of Crystallization Treatment on the Magnetic Properties of Amorphous Strips Based on Co-Fe-Ni-B-Si-Cr Containing Nitrogen

Abstract

Co-Fe-Ni-B-Si-Cr based amorphous strips containing nitrogen were manufactured via melt spinning, and then devitrified by crystallization treatment at the various annealing temperatures of 300℃~540℃ for up to 30 minutes in an inert gas (N2) atmosphere. The microstructures were examined by using XRD and TEM and the magnetic properties were measured by using VSM and B-H meter. Among the alloys, the amorphous ribbons of Co72.6Fe9.8Ni5.5B2.4Si7.1Cr2.6 containing 121 ppm of nitrogen showed relatively high saturation magnetization. The alloy ribbons crystallized at 540℃ showed dramatically reduced remanence and coercive force. A TEM micrograph showed that the grain size of Co72.6Fe9.8Ni5.5B2.4Si7.1Cr2.6 alloy containing 121 ppm of nitrogen was about 5 nm, which exhibited paramagnetic behavior. The formation of nano-grain structure was attributed to the finely dispersed Fe4N particles and the solid-solutionized nitrogen atoms in the matrix. Accordingly, it can be concluded that the nano-grain structure of 5 nm in size could reduce the core loss within the normally applied magnetic field of 300 A/m at 10 kHz.