MICROSTRUCTURE, CHEMISTRY, ELASTIC PROPERTIES AND INTERNAL-FRICTION OF SILCERAM GLASS-CERAMICS

The temperature dependence of both Young's modulus (E) and internal friction (Q-1) from room temperature to 700°C has been determined by Forster's forced-resonance method for three Silceram glass-ceramics, produced by the direct controlled cooling of glass melts in the quaternary system CaO-MgO-Al2O3-SiO2. These results are correlated with microstructural and phase chemistry data as well as calculated viscosity against temperature data. In particular, the viscosity of the residual glass is shown to predominate over its volume fraction in determining the temperature dependence of E and Q-1 for a given Silceram. A simple model which enables the residual glass content of Silceram glass-ceramics to be estimated from a knowledge of the proportions of silicon, iron and magnesium in the corresponding glass melts is also proposed. Furthermore, the room-temperature bulk modulus (K) and Poisson's ratio of two Silceram glass-ceramics are calculated using experimental E and shear modulus (G) values obtained using both Forster's method and another forced-vibration technique.