Tailored Nicrostructures to Control Interfacial Toughness

Abstract

AbstractFailure of ceramic-metal interfaces in response to residual or applied stress is frequently effectively brittle owing to the propensity for interfacial cracking caused by weaker than average chemical bonds and elastic or plastic discontinuities at the interface. Stronger atomic bonding derived from improved interfacial chemistry can enhance fracture resistance to a degree which may be limited by diversion of the crack into the brittle ceramic.Alternatively, methods under study promote interfacial fracture toughness in glass-Cu bonds via near-interfacial microstructures that encourage greater energy dissipation in a region near the interface fracture. Particular success has obtained from microvoid toughening wherein placement of controlled arrays of microcrack-like-voids in the ductile metal, suitably near the interface, can markedly enhance interfacial fracture energy, e.g. by as much as two orders of magnitude and to much greater toughnesses than for glass. The toughness develops with extension of the crack owing to formation of a bridging zone behind the crack wherein the crack flanks are spanned by ligaments of plastically deforming metal film.