Influence of Matrix Composition on Microstructural Yielding and Vickers Hardness in Phase Separated Glasses

Abstract: The relationship between matrix phase composition and microstructure yielding in phase separated calcium aluminosilicate glasses is investigated. Varying the treatment temperature of a phase separated glass results in glasses with different microstructures and matrix compositions. The impact of matrix composition on hardness depends on the mode of microstructural deformation. In glasses that deform via the droplet-densification mechanism, decreasing the matrix silica content results in a decrease in hardness due to the weakest-link effect and greater amounts of incongruent yielding of the phases. This relationship may act as an additional source of the indentation size effect in phase separated glasses. In glasses that deform via droplet-coalescence, decreasing the matrix silica content results in increasing hardness due to increased coalescence of the droplet phase during yielding.