Mechanism of anisotropy in fracture behaviour and fracture toughness of high strength aluminium alloy plate

Abstract

The fracture behaviour and J_Ic fracture toughness of a commercial Al–Zn–Mg–Cu alloy plate has been investigated. Based on the experimental results and available theoretical analyses, the following results were obtained. Secondary grain boundary cracks appeared ahead of the main crack, which served as a triggering mechanism for small scale shearing. Shear failure facets on the fracture surface of single edge notched bend specimens represent the same type of fracture as the fast shear failure that occurred during tensile tests on notched specimens. The grain boundary cracking–small scale shearing mechanism is essentially a type of shielding event that not only makes the fracture appearance obviously anisotropic, but also, to a considerable extent, accounts for the strong anisotropy of fracture toughness.

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