Indentation-induced ductile behavior of glass-ceramics involving layered aluminosilicates

Contact damage in materials is critical in engineering applications because it influences mechanical resistance, such as wear, erosion, and impact failure. Indentation tests were performed using a tungsten carbide ball indenter (Hertzian contact) on the surfaces of glass-ceramics containing hexagonal CaAl2Si2O8 or mica crystals (fluorophlogopite), both of which have a layered structure. The stress-strain relation and the permanent deformation on the surface, as well as the observation of the microcrack zone by X-ray computed tomography using synchrotron radiation, revealed that the glass-ceramic with hexagonal CaAl2Si2O8 showed ductility similar to the quasi-plastic behavior previously observed in the mica glass-ceramic. The yield stresses of the glass-ceramics were estimated from the stress deviating from the stress-strain relation assuming complete elastic response between the ball and the sample. The ratio of the yield stress to Young modulus (Y/E) of the glass-ceramic with hexagonal CaAl2Si2O8 was determined to be higher than that of the mica glass-ceramic.