Fatigue Behaviour in Fine Grained Aluminium Alloys

The effects of alloy production method on microstructure and hence fatigue crack growth rate and fracture mechanism have been examined for a variety of fine-grained/high dispersoid Al-Li-Mg-Zr and Al-Li-Cu-Mg-Zr alloys. Microstructures have been assessed by scanning and transmission electron microcopy, together with electron back scattered diffraction pattern assessment. In these fine-grained/high dispersoid materials, high crack growth rates are seen in comparison to the traditional DC cast alloys, excepting a material with high volume fraction of shearable precipitate. The effects of fracture surface roughness and closure levels in determining crack growth rates has been assessed.