Effect of Si addition on the nano-structure and soft magnetic properties of bulk Fe–B-based alloys

•Addition of Si refines the nano-lamellar spacing in Fe–B eutectic alloy.•Addition of Si improves thermal stability of the nano-lamellar structure.•The soft magnetic properties were improved due to addition of Si.•Nano-lamellar eutectic structures enhance the soft magnetic properties.•The nano-lamellar eutectic structure was obtained in bulk Fe–B–Si alloys.

The effects of Si addition on the nano-eutectic structure and soft magnetic properties of bulk Fe83B17−xSix (x=0–5 at%) alloy rods were investigated. The addition of Si increases the volume fraction of the α-Fe dendrite phase and decreases the average lamellar spacing of the eutectic structure to less than 100 nm. As a result, the intrinsic coercivity (Hc) is decreased effectively, while the saturation magnetization (Ms) remains stable. The annealing experiments of the Fe83B13Si4 alloy show further that addition of a less than 4 at% Si content can improve the thermal stability of the nano-lamellar eutectic structure and the soft magnetic properties.