Influence of Melt Quenching on the Structural Characteristics of a Co–6TiC Alloy

Abstract—The structures and properties of pure cobalt and a Co–6TiC alloy (wt %) fabricated by sintering at 1150°C and melt quenching (MQ) are compared. Cobalt is shown to contain the metastable fcc γ phase along with the equilibrium hcp α phase after both sintering (initial state) and subsequent MQ. MQ results in an increase in the fraction of the nonequilibrium fcc γ phase from 27 to 55%. A single-phase structure based on the metastable fcc γ phase is formed in the Co–6TiC alloy after sintering followed by MQ. Calculations show that, after MQ, the atomic volumes of the α and γ phases in cobalt are lower and those in the Co–6TiC alloy are higher than the atomic volumes of these phases in the materials in the initial (after sintering) state. The microhardness of MQ Co–6TiC fibers more than 50% exceeds that of cobalt fibers due to the following double effect: fcc γ phase stabilization (inherent in TiC even at the usual solidification rate) and enhanced lattice distortion and fragmentation of the matrix and carbide particles after MQ.