Dispersoid and grain size effects on fatigue crack growth in AA2024-type alloys

Fatigue crack growth resistance is known to be influenced by a combination of intrinsic materials behaviour and crack shielding processes. In metallic alloys, shielding due to crack closure is known to be important, however, significant problems exist in experimental determination of closure behaviour. The present work specifically applies detailed, non-subjective closure measurement methods to the assessment of crack growth resistance in 2024-type plate materials. It is shown that whilst the different microstructures exhibited distinct differences in crack growth mode as a function stress intensity level, growth rate variations between the materials were predominantly attributable to closure. Implications for the links between microstructural scale and crack growth processes (extrinsic and intrinsic) are also considered.