Effect of annealing temperature on magnetic properties and corrosion resistance of Fe75.8Si12B8Nb2.6Cu0.6P1 alloy

Abstract Fe-based nanocrystalline alloys obtained through isothermal annealing of their amorphous counterparts have emerged as an indispensable soft magnetic material. The development of Fe-based nanocrystalline alloys with excellent soft magnetic properties and good corrosion resistance is highly desirable. In this study, the magnetic properties and corrosion resistance of Fe75.8Si12B8Nb2.6Cu0.6P1 alloys are investigated a function of the annealing temperature. Upon crystallization, the permeability (μ) and coercivity (Hc) of the alloy gradually improve with an increase in the annealing temperature owing to the formation of homogeneous and fine α-Fe(Si) grains. However, excessively high temperatures promote the precipitation of Fe2B and Fe23B6 phases, significantly deteriorating the soft magnetic properties. The alloy annealed at 843 K exhibits excellent magnetic softness with a high saturation magnetization of 1.41 T, a good μ of 2.7 × 104 at 1 kHz and a low Hc of 0.8 A/m. On the other hand, the corrosion resistance of the alloy is sensitive to the annealing temperature, and the higher the annealing temperature, the better the corrosion resistance will be. The improved corrosion resistance is due to the increase in the crystalline volume fraction resulting in the formation of an insoluble protective layer rich in Si and Nb oxides. This study further reveals the relationship between the annealing temperature and alloy properties and can facilitate the development of soft magnetic nanocrystalline alloys with good corrosion resistance.