High-Temperature Stability of Co-Based Amorphous/Nanocomposite Alloys in Terms of Oxidation and Secondary Crystallization Behavior

This study examined the high-temperature stability of Co-based amorphous ribbons, with a focus on oxidation and secondary crystallization behavior. Five Co-based amorphous alloys with the composition Co75.4Fe2.3Mn2.3Nb4X2B14, where X = Si, Cr, Al, B, or Nb, were evaluated. The primary oxidation products observed were Co3O4 and an internal oxidation zone comprising CoO and FCC-Co. The addition of Si, Cr, and Al was found to enhance corrosion resistance significantly. Furthermore, adding Si, Cr, Al, and Nb increases the transformation temperature and the activation energy for boride formation. Among these elements, Si exhibits the most pronounced improvement in oxidation resistance.