Observations of oxide films on fatigue fracture surfaces of a sintered 2xxx series aluminium alloy

An unusual feature observed in some grain boundaries on the fatigue fracture surfaces of a sintered 2xxx series aluminium alloy is a serrated, film-like structure. Chemical analysis indicates a significant level of oxygen on the serrated features, indicating that they may be oxide films. It is suggested that these films are not a key microstructural feature of the material but are the result of fretting between mating surfaces during fatigue testing.