Amorphous cobalt-base magnetic alloys have found wide applications in transformers, magnetic shields and separators, sensors, computer disk drives, electromagnetic article surveillance systems, satellite components, etc. due to their outstanding properties. These soft magnetic alloys have very attractive properties; namely, relatively high saturation magnetization, very high permeability, significantly low coercivity, ability to achieve near-zero magnetostriction, higher curie temperature compared to Fe- and Ni-base alloys, high electrical resistivity, high yield strength, and good corrosion resistance. The amorphous cobalt-base alloys contain at least one of the elements Fe and Ni, and also at least one metalloid element (Si, B, P, C). The alloys are produced by rapid solidification processing, mainly by the melt spinning technique. Various additional elements may also be added to improve specific properties.
In this study, melt spinning technique has been employed to produce thin ribbons of cobalt-base alloys containing 5 at% Fe and various amounts of Si and B. Precursor materials for melt spinning experiments were prepared by induction melting under a protective atmosphere of argon. Such characterization techniques as Optical Microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Wavelength Dispersive Spectroscopy (WDS-SEM) were employed to study the influence of Si and B contents on the microstructure of ingots and ribbons. Magnetic properties of melt-spun ribbons were determined using Vibrating Sample Magnetometer (VSM) and Static Hystersisgraph.
The microstructure of quaternary ingots were found to be composed mainly of Co-based solid solution and intermediate compounds CoXSi (X?2) and CoYB (2<Y<4). In all these phases, a number of iron atoms have occupied a proportion of cobalt sites in their crystal lattice. Boron has a more significant effect compared to silicon in modification of the ingots microstructure.
Furthermore, the higher the total amounts of Si and B as well as B/Si ratio (within the investigated range), the superior the quality and amorphousness of the melt-spun ribbons. The results of magnetic property measurements revealed that an increase in boron and silicon contents of the alloys leads to a decrease in coercivity, Hc, and saturation magnetization (induction), Ms (Bs) of the ribbons. And also in constant total Si and B content, the greater the B/Si ratio, the greater the Bs and Br of melt spun ribbons.