Influence of structure on soft magnetic properties of Co ₇₀Fe ₅Si ₁₅B ₁₀ metallic glass ribbons

Purpose: The paper presents a structural, thermal and magnetic characterization of Co-based amorphous samples in as-cast state and after annealing process. Design/methodology/approach: The studies were performed on Co ₇₀Fe ₅Si ₁₅B ₁₀ metallic glass in form of ribbons with different thickness. The amorphous structure and phase analysis of studied samples after annealing process was examined by X-ray diffraction (XRD). The crystallization behaviour of the studied ribbons was also examined by differential scanning calorimetry (DSC). The fracture morphology of the ribbons after heat treatment was analysed using the scanning electron microscopy (SEM). The soft magnetic properties examination contained relative initial magnetic permeability and magnetic permeability relaxation measurements. Findings: The X-ray diffraction investigations revealed that the tested ribbons with different thickness were amorphous. The two exothermic peaks describing crystallization process of Co ₇₀Fe ₅Si ₁₅B ₁₀ alloy were observed for all studied samples with different thickness. The heat treatment process of ribbon samples involved crystallization of α-Co(Si), Co ₂Si phases and cobalt borides at temperature above 773 K. The study of fracture morphology of samples after annealing at 623 K shows mixed fractures with "river" patterns, which are characteristic for glassy materials and some areas of scaly morphology. The initial magnetic permeability decreases in function of the increase of annealing temperature, but a local maximum could be determine at 673 K. Practical implications: The soft magnetic properties of studied metallic glasses can be formed by different sample thickness and applying the appropriate conditions of annealing process. Originality/value: The applied investigation methods are suitable to determine the changes of structure and soft magnetic properties of examined Co-based alloy with function of sample thickness and heat treatment conditions.