Influence of microstructure on fatigue crack propagation behaviors of an aluminum alloy: Role of sheet thickness

•The influences of 30mm and 55mm sheet thickness on fatigue propagation behaviors (including fatigue crack propagation rate, microstructure, fracture analysis, crack propagation morphology) in alloy were analyzed contrastively.•The influences of precipitation strengthening phase, coarse particles, grain boundaries, sub structure, grain micro orientation and other microstructure on fatigue crack propagation behaviors were analyzed and discussed in detail, respectively.