The competition between intergranular and intragranular fracture is investigated using a bilayer damage model, which incorporates the relevant, microstructural features of aluminum alloys with precipitate free zones (PFZ) nearby the grain boundary. One layer represents the grain behavior: due to precipitation, it presents a high yield stress and low hardening exponent. The other layer represents the PFZ which has the behavior of a solid solution: much softer but with a much higher hardening capacity. In both layers, void growth and coalescence is modeled using an enhanced Gurson-type model incorporating the effects of the void aspect ratio and of the relative void spacing. Qualitative understanding of trends in the ductility fracture toughness of aluminum alloys can be gained in order to provide a link with the thermal treatment process.
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