Structure and magnetism of Fe-26Cr-12Co-1Si ribbon magnets

This paper provides a new and simple way to obtain thinner ribbon magnets with hard magnetic properties. Fe-26Cr-12Co-1Si ribbons were fabricated by melt-spinning at a speed of 40 m/s and followed by multi-step ageing at 647–540 °C. Phase composition, microstructure, domain structure and magnetic properties of the ribbons were studied. It has been found that the phase transformation of γ+α→α₁+α₂+ Fe(Si,M)₂+σ and element diffusion are dominant respectively during the first stage ageing and later multi-step ageing. Consequently, a spinodal structure containing a majority of α₁ and small amount of α₂ is formed. Model for microstructure and magnetic structure evolution of the ribbons in the ageing process is established. Hc as high as 1026.6 Oe and Br of 7274.8 Gs can be achieved in the seven-step aged ribbons. Such outstanding magnetic performances may be attributed to five main microstructural and magnetic structural factors. - Highlights: • Hard magnetic Fe-Cr-Co-type ribbons were prepared by melt spinning combined with heat treatment. • Lorentz TEM was used to observe the domain structure. • The microstructure and domain structure were investigated and corresponding models were built up. • The coercivity as high as 1026.6 Oe can be achieved. • Five main factors contribute to the excellent magnetic properties.