Microstructure and mechanical properties of MgO–Al2O3–SiO2–TiO2 glass–ceramics

Crystallization sequences of MgO–Al2O3–SiO2–TiO2 system glass were investigated by means of DTA, XRD, SEM and EDS. The mechanical properties of samples, including density, microhardness and elastic modulus, were characterized as well. The relationship between crystalline phases, heat treatment methods and mechanical properties is discussed. The results have shown that: the glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phase. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss, α-cordierite and cristobalite made their appearance successively. When the glass was heated at 1100 °C for 2 h, the maximum elastic modulus of 137 GPa (accompanied by a microhardness of 8.5 GPa and a density of 2.924 g/cm3) was obtained.