Microstructure, thermal stability and soft magnetic properties of Fe81B10P8Cu1 amorphous/nanocrystalline alloy refined by slags with low basicity

•Utilizing refining slag with low basicity is beneficial for impurity removal and soft magnetic properties.•The purified alloy has an increased proportion of α-Fe-like structure, which can refine the nanocrystals during annealing.•The ΔTx of amorphous alloy increases after purification.•Effect of refining slag on microstructure of amorphous alloy is investigated by Mössbauer spectroscopy. The amorphous/nanocrystalline duplex structure is stable and exhibits excellent soft magnetic properties. However, the presence of impurities inevitably impacts the performance of the products. In this work, the impact of refining slags with various basicities (R=1, 0.66, 0.5, 0.4) on the microstructure, thermal stability, and soft magnetic properties of Fe81B10P8Cu1 alloy was investigated by varying the composition ratio x:1:1 (x = 2, 3, 4, & 5) of B2O3:MnO:MgO. The utilization of refining slag with low basicity is beneficial for removing impurity, enhancing magnetic exchange interactions and reducing magnetic anisotropy in amorphous alloy, thereby improving its soft magnetic properties. Notably, when the refining slag composition of B2O3:MnO:MgO is 4:1:1, the Fe81B10P8Cu1 nanocrystalline alloy exhibits exceptional soft magnetic properties and the smallest grain size, with a Bs of 1.717 T, Hc of 3.85 A/m and an average grain size of 23.84 nm. These findings are significant for enhancing the performance of Fe-based nanocrystalline alloys.