A novel experimental set-up for warm incremental forming of AZ31B magnesium alloy sheets

Incremental sheet forming operations are more and more widespread thanks to their intrinsic flexibility and applicability to a wide range of metallic materials. However, even if this kind of processes can assure a significant increase in material formability compared to traditional sheet forming operations, their application to magnesium alloys is still troublesome. Magnesium alloys, indeed, shows very limited ductility when processed at room temperature, and their formability can be extended only if the sheet is heated up in a temperature range where more slip systems can be activated. The paper presents a novel experimental set-up specifically developed to carry out incremental forming operations at elevated temperatures. The set-up includes a CNC machine and an electric heating system. When the current flows to the metal sheet, heat is generated and the local material formability is enhanced. Different tests were carried out in order to design the proper parameters of the heating system, assuring a sufficiently homogenous temperature in the sheet, measured through spot-welded thermocouples. It is demonstrated that carrying out the process in the temperature range between 150° and 250°C can assure a higher formability than at room temperature. It is demonstrated that material formability in terms of maximum wall angle is mainly affected by the initial sheet temperature, while the step down size mainly influences the quality of the part inner surface.