Crack growth in AA6060 after two and eight equal-channel angular extrusions (ECAE),
showing a bimodal microstructure and a homogenous ultrafine-grained microstructure, respectively,
are compared to the coarse grained counterpart. Furthermore, an optimized condition, obtained by
combining one ECA-extrusion and a subsequent short aging treatment is included. Fatigue crack
growth behaviour in the near-threshold regime and the region of stable crack growth is investigated
and related to microstructural features such as grain size, grain size distribution, grain boundary
characteristics and ductility. Micrographs of crack propagation surfaces reveal information on crack
propagation features such as crack path deflection and give an insight to the underlying
microstructure. Instrumented Charpy impact tests are performed to investigate crack initiation and
propagation under impact conditions. Due to the recovery of ductility during the post-ECAE heat
treatment, the optimized condition shows improved fatigue crack properties and higher energy
consumption in Charpy impact tests, when compared to the as-processed conditions without heat
treatment.