Influence of microstructure-driven strain localization on the ductile fracture of metallic alloys

Most models in the literature that are used to understand and predict ductile failure, ductility or fracture toughness implicitly consider that the plastic response of the material is homogeneous at the level of the microstructure. However, in a number of situations, plasticity is intrinsically localized, because the microstructure is spatially heterogeneous, or because the loading leads to strain localization on the microscale, such as in fatigue loading, or because the dynamics of plastic flow are unstable, such as in Portevin-Le Chatelier instabilities. This paper presents, from analysing various examples, the influence of these strain localization phenomena on the ductile fracture behaviour of metallic alloys. Examples to illustrate these effects will be chosen from, firstly, internal necking between cavities growing to ductile fracture, secondly, damage mechanisms from fatigue persistent slip bands, thirdly, the effect of Portevin-Le Chatelier bands on toughness and, fourthly, damage mechanisms in alloys with precipitate-free zones at grain boundaries.