A comparative study on nanocrystalline soft magnetic Fe-Si-B-Nb-Cu alloys made of pure elements and ferro-alloys

•Flux-shielded air induction melting process was used to prepare this alloy which not only avoids oxidation but helped to remove impurities thereby purifying the alloy.•Impurities present in the commercial grade alloy does not affect the glass forming ability.•Impurities affected the thermal properties by altering the onset of phase transformation temperature however resultant by products of phase transformation were not changed.•The high activation energy of Fe3Si phase in commercial grade alloy has resulted in low volume fraction and high grain size of Fe3Si phase.•The amorphous phase Curie temperature decreased in commercial grade alloy due to the decrease in exchange interaction because of decrease in Fe-Fe distance.•The soft magnetic properties remain almost same for both alloys prepared using pure elements and commercial grade alloys and the soft magnetic properties are independent of type and nature of impurities. In the present study, we report a cost-effective method of flux-shielded air induction melting using commercial grade master alloys to produce nanocrystalline soft magnetic Fe73.5Si13.5B9Nb3Cu1 alloy. For comparison, the alloy was made from highly pure raw materials as well. The structure and soft magnetic properties of the commercial grade alloy is similar to the pure one. Air induction melting process with flux not only removed impurities through chemical reactions, it also provided protection from oxidation. Studies of glass formation through experimental findings and Glass Forming Ability (GFA) calculations through ΔT value, α-parameter and PHSS parameter and studies using Calphad (Calculation of Phase Diagram) method have shown that the impurities present in the commercial grade alloy did not affect the glass formation compared to the pure grade alloy. Impurities present in the commercial grade alloy increase the activation energy of crystallization of Fe3Si phase, which in turn influences the volume fraction and grain size of Fe3Si phase during annealing treatment. Amorphous phase Tc was found to decrease due to the impurities present in the amorphous phase and this decreased exchange interaction between Fe-Fe atoms. Saturation magnetization and coercivity of commercial grade alloy are almost equivalent to the alloys prepared with pure elements and they are independent of type and concentration of impurities. Lowest coercivity in commercial grade alloy can be achieved in less annealing time which can lead to increase the productivity