Elastic after-effect in WC/Co cemented carbide

Free-decay internal friction measurements as a function of temperature and frequency have been used to study the inherent viscous behavior of the Co binder present at grain boundaries of a WC/Co cemented carbide material. The presence of a relaxation peak was related to the micromechanism of anelastic grain-boundary sliding and a peak-shift analysis was presented as a function of frequency. Using the mechanics of the elastic after-effect, both the viscosity and the activation energy of the intergranular Co binder could be determined. A comparison of the intergranular viscosity data was carried out with data obtained on bulk Co metal both in the high-purity state or in solid solution with a small volume fraction of WC. The viscosity of the Co binder, as determined by internal friction, showed good agreement with the bulk Col WC solid solution, whose chemical composition was presumably the closest to the intergranular binder in the cermet material. Based on the agreement between intergranular and bulk viscosities as well as activation energy values, it is considered that the present method can be more generally used in ceramic/metal materials. (C) 1999 Elsevier Science Limited. All rights reserved.