Abstract
The fracture behaviour of a peak-aged, partially recrystallized Al–4·5Cu–1·21Li–0·51Mn–0·20Cd alloy has been investigated as a function of strain amplitude, stress intensity, and environment. It was found that the failure was predominantly intergranular separation, regardless of the environment, stress intensity, or strain amplitude, and that the fracture behaviour was influenced mostly by intrinsic microstructural features, rather than the nature of the environment. The shearable nature of matrix strengthening precipitates, large recrystallized grains, and precipitate-free zones along the high-angle grain boundaries aid in localizing the deformation, resulting in low-energy intergranular fracture. The iron- and silicon-rich intermetallic precipitates in the alloy promote void nucleation following fracture of the particle. A model is proposed which suggests the need for high stresses and strains for the initiation and spontaneous growth and coalescence of microvoids. The mechanisms of fracture behaviour of the alloy are discussed in terms of several concurrent processes involving strength of the material, intrinsic microstructural effects, deformation behaviour, state of stress, and strain.
MST/497
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