INFLUENCE OF A CHANGING MICROSTRUCTURE ON HIGH-TEMPERATURE RELAXATION PEAKS, AN EXAMPLE - WC-11WT-PERCENT-CO

WC-11wt.%Co cemented carbide exhibits a relaxation peak at about 920 K in the 1 Hz frequency range. However, the values of the relaxation parameters are unusual. The apparent activation energy is higher than the selfdiffusion energy and increases with the temperature from 3.5 eV to 7 eV. The apparent limiting relaxation rate of 10(35) s(-1) is much too high in comparison with a lattice vibration frequency. Moreover, superimposed on the relaxation peak, an extra damping is detected which is due to the heating or cooling rate (T effects). These phenomena can be interpreted as due to the evolution of the microstructure during the internal friction measurements. Effectively, taking into account the microstructural modifications, it is possible to modify the classical equation for dislocation damping in order to predict the shape of the associated relaxation peaks. Generalization of this approach can supply a method for analysing the damping peaks which present non-classical characteristics.