Formability of 7000 aluminum alloys in warm and hot forming condition

Abstract

In recent years, the automobile industry has been calling for new lightweight solutions to fulfill increasing ecologically requirements. A weight reduction of automobile body constructions is necessary to reduce fuel consumption and CO2 emissions. In order to reach this aim, new materials and novel forming processes are required. Also, the importance of aluminum alloys in the automobile industry is constantly increasing. Nowadays, mainly alloys of the 5000 and 6000 aluminum series are used for structure parts or shell parts, respectively. Another alloy series are the 7000 aluminum materials. These alloys offer a great lightweight potential due to their high specific strength combined with a moderate ultimate elongation. Nevertheless, these alloys are not yet widely used in the automobile industry. The reason is the limited formability of 7000 aluminum at room temperature in high-strength heat treatment condition. There are two approaches to increase the formability based on elevated temperatures, specifically the two processes of warm and hot forming at temperatures lower than the recrystallization temperature or above it, respectively. This paper deals with the investigation of the influence of forming conditions, especially the forming temperature. Trapezoidal parts were deep-drawn at different forming temperatures and subsequently investigated by determining the deformation with an optical measurement system as well as the springback of the material. In addition, the influence of the forming temperature on the flange feed was investigated as well as the influence of the paint bake process on the artificial aging step. Results show, that the formability increases with increasing forming temperature in the warm forming process route. Also, the artificial aging time can be decreased by a combined aging with paint bake heat treatment.