Metal ceramic interface toughness II: Mechanisms of fracture and energy dissipation

Abstract

Based on observations of plasticity on fracture surfaces, we propose two fracture mechanism for Ni-sapphire interfaces. A brittle-type mechanism is proposed for the decohesion of Ni from sapphire by which cracks advance in increments of 20 nm. When particulates that increase the interface strength are present, debonding occurs at the leading edge of the particulate, and unsteady crack advance occurs. Additionally, toughening mechanisms are proposed for each type of plasticity feature observed, and the fracture energy of each mechanism is quantified. Comparison of energy dissipated by these mechanisms with measured fracture energies indicates how the fracture energy of the interface varies with sulfur segregation and environmental embrittlement.