Synergistic effects of Si, B and P on microstructure and magnetic properties of Fe-Si-B-P-Nb-Cu alloys

•The contents of Si, B and P have great influence on the crystallization behavior.•A moderate P and Si/B ratio is the key to obtaining good soft magnetic properties.•The ability of grain refinement decreases in the order of P ˃ Si ˃ B.•Increasing P and Si/B ratio can effectively reduce the average size of α-Fe(Si) grains. Metalloid elements significantly affect the microstructure and magnetic properties of Fe-based nanocrystalline alloys. However, adding multiple metalloids would complicate the impact of each metalloid on magnetic properties. Here, we have found that Fe81.3SixByP17-x-yNb1Cu0.7 nanocrystalline alloys exhibit high saturation magnetic flux density (Bs) of 1.73–1.79 T and low coercivity (Hc) of 4–6 A/m. It was found that Si, B and P elements have strong synergistic effects on the thermal stability, magnetic properties, microstructure and crystallization kinetics of the alloys. Keeping the P content and Si/B ratio at a moderate level is the key to obtaining an ultrafine nanocrystalline structure with high Bs and good soft magnetic properties. The underlying mechanism by which the addition of multiple metalloids affects the microstructure and magnetic properties has been revealed.