Mechanical properties and deformation mechanisms of phase-separated soda-lime-silica glass

Abstract

The possibility that liquid phase separation enhances mechanical properties of glasses has recently garnered interest, yet questions persist regarding the mechanisms underlying these effects and their correlation with two-phase glass microstructures. To address these questions, the present study investigates some mechanical properties and the deformation response of a phase-separated soda-lime-silica glass with varying microstructures ranging from nanosized, interconnected to larger, dilute droplet structures. By maintaining a constant chemical composition, the direct influence of the microstructure morphology on certain mechanical properties is probed. Electron microscope images of crack tips reveal that the secondary phase can deflect and bridge propagating cracks in both interconnected and droplet microstructures, which is further confirmed by peridynamic simulations. Raman spectra show characteristic peak shifts of both amorphous silica and soda-lime glass during deformation, indicating a combined contribution of matrix and secondary phase. Notably, the interconnected structures exhibit smaller deformation zones, and cracks generated by low force indentations are significantly shorter compared to the droplet structures. These observed nanostructural effects lead to a 20 % increase in indentation fracture toughness and up to 40 % increase in flexural strength in interconnected structures. The increase in strength and toughness appears to be mainly related to the ability of certain morphologies to absorb stresses through densification of the secondary phase and to decrease the opening force of propagating cracks through crack deflection on interfaces.