Processing of lithium aluminium silicate glass-ceramics and investigations of fracture behaviour and its correlation with the microstructural features

Lithium Aluminium Silicate (LAS) samples were fabricated through a melt casting process using Lithium carbonate, Aluminium hydroxide, Silica and other additives as raw materials. The melt was drain casted at 1300 degrees C in a pre-heated mould followed by annealing and ceramization at 850 degrees C. Ceramized samples were subjected to X-ray diffraction. The density of the samples was found to be in the range of 2.53-2.54 g/cm3. The sample was found free from bubbles and inclusions after optically polishing. Mechanical properties including hardness, flexural strength, fracture toughness and compressive strength of LAS samples were evaluated. Knoop hardness of the LAS samples was found to be 597-669 kg/mm2. LAS sample exhibited a peak flexural strength of 110-114 MPa and compressive strength of 221 MPa before fracture. Additionally, the total fracture energy release rate (Jc) of LAS samples along with R-curve and fractography were also studied. R-curve exhibited an increasing trend of Jc with respect to normalised displacement without any sign of saturation indicating the scope for optimisation of quantification of crystals fraction in the glass matrix to obtain the predominant toughening behaviour. Finally, the physico-chemical, microstructural and optical properties were measured and correlated with the mechanical properties observed. Near to theoretical density, high crystallinity and superior mechanical properties of processed LAS glass-ceramic can be used in strategic and civilian applications.