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The competition between intergranular and transgranular ductile fracture in Al
alloys with precipitate free zones is investigated using a multiscale FE based
approach. The solid is represented by discrete grains. Each grain is made of
harder interior core and softer grain boundary layers, each region being
discretized with many elements and represented by different hardening and
damage related parameters. The material behaviour is given by an advanced
micromechanical damage model for the transition to the smallest scale. This
model relies on the extension of the Gurson model by Gologanu while introducing
a new void rotation law and a new generalized void coalescence model.
Homogenous biaxial loading, tensile testing with necking and crack propagation
from a precrack are simulated to investigate the relationships between the
hardening law, microstructure parameters, stress state, fracture mechanisms and
fracture resistance expressed by a fracture strain or a JR curve.