Fatigue resistance of light alloy sheets undergoing eco-friendly chemical milling: metallurgical and chemical aspects

Component lightening is a key issue for automotive and aerospace industries. Lightening processes on design profile are not always possible by means of traditional machining processes. Then, chemical milling processes are used, often by acid etching. The effect on fatigue behavior is related on many factors, such as chemical surface composition and surface roughness. Material removal through chemical milling is in particular interesting for Additive manufactured components where surface finish still remains a parameter difficult to be controlled and repeated. The environmental aspects related to alkaline and acid processing are still an important issue. In the present paper, an overview on chemical milling for component lightening is presented with focus of the effects on mechanical and chemical resistance of materials. Then, the results of an experimental campaign on an aluminum alloy is presented. In particular, high cycle fatigue tests results are presented on specimens subjected or not subjected to an eco-friendly alkaline chemical milling process (called " Green Etching") and chemical, profilometric and metallographic analyses are presented and related to fatigue resistance results. Wettability and surface charge results will be presented.