Temperature Controlled Forming of 7075-T6 Aluminum Using Linearly Decaying Direct Electric Current

The push in the automotive industry towards lightweighting to meet new stricter fuel efficiency standards has driven the need to research lightweight material forming. This requires research into forming high strength materials, as well as lower strength lightweight materials that may typically have poor formability characteristics. 7075-T6 aluminum suffers from limited elongation during tensile forming; electrically-assisted forming, which uses direct current to improve formability, is a viable candidate process to improve formability. In past electrical tension testing by various authors, two types of wave forms have been examined: continuous current and square waveforms. For tension it was shown that applying current using square waveforms was able to extend formability beyond what continuous current could produce, due to reducing the overheating in the necking region. This paper examines the effect of a non-decaying and linearly globally decaying saw tooth wave on the formability and flow stress of 7075-T6 aluminum in tension. It is shown that EAM using a sawtooth waveform can result in further elongation than cold forming, with similar elongation to previously-investigated square waves. An existing temperature model is adapted to the saw tooth waveform and used to calculate the change in material properties to find the flow stress using a theoretical strength equation.