A review of sheet warm forming methods for high-strength 7xxx aluminum alloys

The article presents an overview of the warm forming process used to form 7xxx alloy sheets. The literature review covers the characteristics of alloys tested during forming at elevated temperatures: AA7075, AA7020, and a non-commercial alloy with a lower chromium content, higher zirconium content, and higher zinc-to-magnesium ratio than commercial alloys. A diagram of the forming process is presented, taking into account the individual stages and the most important parameters of heat treatment and deformation. An analysis was carried out of the results published to date in the field of basic research, such as tensile tests of alloys in the temperature range of 20–300°C, limiting dome high and limiting drawing ratio tests in the temperature range of 20–260°C, and tests of forming blanks such as a bracket, U-profile, lower part of a B-pillar, and B-pillar. Based on an extensive literature review, it can be concluded that warm stamping with accelerated heating allows for achieving at least 90% of the original strength of the AA7075 alloy. The use of a paint baking process (heat treatment at 180°C for 30 min) after stamping can contribute to a final product strength of up to 85–90% of the strength of the alloy in the T6 state.