On fracture anisotropy in textured aluminium alloys

The yielding, plastic flow and fracture of textured aluminium alloys depend on their microstructure formed during the thermo-mechanical processing. In this work, we investigate two extruded aluminium alloys with different yield strength, work hardening, grain structure, crystallographic texture and tensile ductility. To study the fracture anisotropy of these alloys, i.e., the variation in the failure and fracture strain with loading direction, finite element simulations of an axisymmetric smooth tensile specimen are compared to experimental tests in five in-plane directions with respect to the extrusion direction. A newly proposed coupled damage and single crystal plasticity model is used in three-dimensional finite element analyses of the tensile tests. The tensile tests are simulated in Abaqus/Explicit, where each grain is explicitly modelled. This modelling framework is able to capture the effects of the heterogeneous yielding and plastic flow on ductile fracture, caused by the differences in the crystallographic orientation between grains, such as shear bands which may promote strain localization and ductile fracture. The overall agreement between the experimental and numerical results with respect to the plastic anisotropy, i.e., the anisotropy in yielding, plastic flow and work hardening, highlights the important role played by the crystallographic texture. Plastic anisotropy is found to have a marked influence on the tensile ductility and to induce fracture anisotropy. By particularly accounting for the crystallographic texture, the finite element simulations are able to capture the fracture anisotropy observed in the experimental tests.