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The competition between intergranular and intragranular fracture isinvestigated using a bilayer damage model, which incorporates the relevantmicrostructural features of aluminum alloys with precipitate free zones (PFZ) nearby thegrain boundary. One layer represents the grain behavior: due to precipitation, it presentsa high yield stress and low hardening exponent. The other layer represents the PFZ whichhas the behavior of a solid solution: much softer but with a much higher hardeningcapacity. In both layers, void growth and coalescence is modeled using an enhancedGurson-type model incorporating the effects of the void aspect ratio and of the relativevoid spacing. Qualitative understanding of trends in the ductility fracture toughness ofaluminum alloys can be gained in order to provide a link with the thermal treatmentprocess.