Macroscopic shear localization and fracture of notched and unnotched Al–Zn–Mg–Cu bars

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Abstract
Tensile tests of notched and unnotched Al–6Zn–2·3Mg–1·7Cu alloy bars have been carried out. The underaged and peak-aged unnotched specimens exhibit macroscopic shear localization during testing, followed by shear failure, whereas the overaged unnotched specimens exhibit the conventional ‘cup–cone’ mode of failure. The introduction of a notch changes the deformation pattern and the fracture mode of the specimens. Deformation is constrained within the notched region, and the triaxial tensile stress developed at the notch results in grain boundary splitting, which complicates the deformation pattern and failure mode. The fracture behaviour of these specimens is explained by an adaptation of crystal slip theory. MST/197