Recent progress on co-base alloys - Phase diagrams and application

Abstract

This paper presents recent progress on the phase diagrams and design for Co-base alloys, focusing on magnetic recording media, ferromagnetic Co-Ni-Al-base shape memory alloys, half-metallic Heusler alloys and Co-base superalloys. The calculated miscibility gap between ferromagnetic and paramagnetic states in the Co-X(X: Cr, Mo, W) systems has been found to agree well with the experimental results, strongly implying that the magnetic induced phase separation is responsible for the compositional heterogeneity in Co-base magnetic recording media. New ferromagnetic Co-Ni-Al shape memory alloys have also been developed based on phase diagrams, where the introduction of γ(Al structure) to the (β(B2) matrix was found to drastically improve the ductility. The phase stability of half-metal Heusler Co-Cr base alloys is discussed in relation to the order-disorder transition, Curie temperature and the spin polarization ratio. Finally, the possibility of potent strengthening of Co-base superalloys by precipitation of the y'CLU) phase is presented.