Effects of precipitate and crystal orientation on the magnetic properties of non-oriented FeSi steel components upon aging process

Three non-oriented FeSi steel samples with varying carbon contents (0.41 wt% C, 0.18 wt% C, and 0.05 wt% C) were subjected to thermal aging to investigate the combined effects of carbon content and preferred crystal orientation on magnetic performance. In the initial state, the 0.18FeSi sample exhibited the steepest hysteresis curve and the lowest average coercivity (Hc ≈ 115 A/m), attributed to its high cumulative density of < 100 > components, particularly {hkl}<100> (η-fiber) component. Saturation magnetization (Ms) varied across directions and compositions, with the 0.05FeSi sample consistently showing the lowest Ms, likely influenced by variations in its alloying elements. After aging at 180 °C for 20 days, the 0.41FeSi sample exhibited flattened hysteresis curves and a significant increase in Hc, while the 0.18FeSi sample showed an Hc increase but retained a steep curve. The 0.41FeSi sample formed a high density of ~ 2 μm iron-carbide precipitates, whereas the 0.18FeSi sample had fewer, smaller precipitates (~ 1.6 μm); no precipitates were observed in the 0.05FeSi sample. The precipitate-matrix orientation relationships likely follow the Baker-Nutting or Pitsch model, promoting nucleation along the [110] and [100] planes. Despite having the highest density of {100}< uvw > and {hkl}<100 > fibers after aging, the 0.18FeSi sample exhibited increased Hc while maintaining a steep hysteresis curve. These findings indicate that while favorable texture improves magnetic performance, the presence of precipitates-depending on their density and size-can partially degrade coercivity and overall magnetic behavior after aging.