Abstract
The high Machinability of Mica glass-ceramics is due to its unique microstructure. This study investigated barium fluormica glass-ceramics, with reference to parameters, which determine the microstructure that governs Hardness and machinability and explore the validity of Baik's model for high mica Volume Fractions. Barium fluormica glasses were synthesized and casted into rods then heat-treated at 1175 degrees C and 1200 degrees C for various times. Glass-ceramics were characterized using DSC, SEM, Vickers microhardness and machinability test. "House of Cards" microstructure was successfully obtained upon heat treatment and was associated with an increase in Volume Fraction and Aspect Ratio of crystals. The Volume Fraction was almost identical for all the samples. However, crystal length and width increased with increasing holding time. Hardness and machinability forces decreased with increasing the Aspect Ratio and Effective Crystallinity. Hardness and Machinability data agreed well with Baik's data and extend the validity of Baik's model to much higher Volume Fractions.