Indentation Deformation and Fracture of Sapphire

摘要: Relatively little is known about the fundamental deformation processes in intrinsically hard, brittle materials, and even less how these lead to initiation of cracks. In this paper, transmission electron microscopy used study structure within Vickers indentation zones single-crystal sapphire with {} surface orientation. The relative misorientation regions zones, as mapped by convergent-beam kikuchi patterns, found be severe, indicative shear operating close cohesive limit. Two principal types are identified, basal twinning pyramidal slip. Incipient microcracks observed at both twin interfaces slip planes. These incipient “flaws” act nucleation sites for ensuing radial lateral