Quantitative assessment of the impact of second phase particle arrangement on damage and fracture anisotropy

The fracture anisotropy of the three aluminium alloys Al 6056, Al 6061 and Al 6005A has been characterized in tension. In the three alloys, the onset of yielding and strain hardening behaviour do not significantly depend on the loading direction. However, while the fracture strain is close to isotropic in the alloys Al 6061 and Al 6005A, the alloy Al 6056 exhibits clear fracture anisotropy. In situ tensile tests in X-ray tomography reveal that there exist two coalescence stages that include intra-and inter-cluster coalescence. A quantitative approach is proposed to relate the propensity to fracture anisotropy to a simple microscopic parameter characterizing the degree of anisotropy in the spatial distribution of second phase particles. The new indicator which quantifies the degree of connectivity or percolation between clusters is successfully assessed for the three Al alloys. (c) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.