Elevated temperature forming limit strain diagrams of automotive alloys Al6014-T4 and DP600: A case study

Abstract

The press formability of the automotive materials such as aluminum alloys, magnesium alloys and steels is influenced by forming temperatures. While adjusting the temperature level of die, punch and binder, the lightweight materials can successfully be formed, especially for complex automotive body parts. The objective of this case study is to determine the forming limit curves of Al6014 and DP600 alloy sheet at elevated temperatures in specific range of 200 °C and 250 °C suitable for press operation in long-run production cycles. The focus is set on Al6014 and DP600 as these two materials are widely used in automotive panels due to their high strength and lightweight and improved resistance to corrosion. DP600 is sometimes preheated before forming to avoid cracks. Thus, it is essential to study the effect of preheating temperature on the formability. Experiments were conducted at forming temperatures of 200 °C and 250 °C and at low punch speed. The measurement of train distribution was carried out online using digital image correlation with the optical deformation measurement system GOM Aramis. Both Al6014 and DP600 alloys were found to have good drawability and stretchability. It was found that for Al6014, the forming limit curve level increases with temperature. On the contrary, DP600 showed slight decrease in the level of forming limit curve as temperature was increased. Warm formability for these alloys was further characterized through part depth and percentage thinning measurements.