Microstructures and fatigue fracture behavior of an Al–Cu–Mg–Ag alloy with addition of rare earth Er

The effects of rare earth erbium (Er) on microstructures and fatigue fracture behavior of an Al–Cu–Mg–Ag alloy were investigated. Microstructural examinations first revealed that the precipitation kinetics of Ω phase was distinctly retarded by promoting the formation of θ′ phase with the Er addition during the initial aging. The fatigue crack propagation resistance of Er-containing microstructure was significantly enhanced arising from the presence of the crystallographic secondary cracks, which was directly relative to the large grain size. Results also suggested that the dendritic substructure of as-cast Al–Cu–Mg–Ag alloy was refined remarkably by Er addition.