High-performance gradient Fe-Si alloy thin sheets fabricated by solid powder siliconizing and diffusion annealing

A gradient Fe-Si alloy was prepared by solid powder siliconizing and diffusion annealing using Fe-3.0 wt% Si alloy as raw material. Solid powder siliconizing was carried out at 800 °C for 10–20 min, and siliconized samples with Fe3Si phase and FeSi phase were obtained. Then, the siliconized sample was subjected to diffusion annealing at 1050 °C for 1–2 h, and the Fe3Si phase and FeSi phase were transformed into single α-Fe phase. The magnetic properties of gradient Fe-Si alloys are higher than those of Fe-Si alloys with uniform Si content distribution (even Fe-6.5 wt%Si alloy). When the surface Si content is 12.3 wt% and the core Si content is 5.0 wt%, the iron loss of the gradient Fe-Si alloy at high frequency is reduced by 97.3% compared with Fe-3.0 wt%Si alloy. Moreover, gradient Fe-Si alloys show excellent magnetic induction intensity and mechanical properties after solid powder siliconizing and diffusion annealing process. This work proposes a solid powder siliconizing and diffusion annealing method to prepare high-performance gradient Fe-Si alloys, which is simple, low-cost, and can control the distribution of Si content in the thickness direction, providing a new idea for the realization of large-scale industrial production of high-performance Fe-Si alloys.