Experimental and Theoretical Investigation on the Forming Limit of 2024-O Aluminum Alloy Sheet at Cryogenic Temperatures

Cryogenic forming, a new technology used to manufacture aluminum alloy thin-walled parts, has attracted much attention in recent years. This work presents an experimental and theoretical study of 2024-O aluminum alloy sheet forming limit at cryogenic temperatures and provides an effective method for accurate prediction of forming limit curves (FLCs) at cryogenic temperatures. Uniaxial tensile experiments at different temperatures were carried out between 20 °C and − 196 °C to obtain the constitutive equation of the material at cryogenic temperatures. The Marciniak–Kuczynski (M–K) model was used to predict FLCs at cryogenic and room temperatures. The constitutive equation and yield functions are used in the model. The effects of different yield criteria (Mises, Hill-48, Barlat89, Gotoh, and Yld2000-2d) on the prediction results of FLC are analyzed. These prediction results were verified by the Nakazima test, and it was found that the Yld2000-2d yield criterion is the most accurate for FLC prediction. Finally, the M–K model is combined with this criterion to predict the FLC at different temperatures. It was found that the lower the temperature, the higher the FLC curve and the better the sheet formability, and the increase is more obvious at extremely low temperatures.