The identification of improved Johnson-Cook constitutive model in a wide range of temperature and its application in predicting FLCs of Al-Mg-Li sheet

For the Al-Mg-Li alloy sheet, a series of uniaxial tensile tests are firstly carried out under different temperatures (25-450 degrees C) and strain rates (0.00025-0.01 s(-1)). Then, to describe the flow behavior of the sheet, the improved Johnson-Cook constitutive model (hereinafter abbreviated as 'improved J-C model') is employed, in which the coefficients are respectively determined in different temperature ranges of 25-150 degrees C, 200-300 degrees C and 350-450 degrees C. Afterwards, the improved J-C model is introduced into the modified M-K model to predict the FLCs of the sheet, which are finally compared with the experimental FLCs obtained by Nakazima tests. It is found that the improved J-C model can accurately describe the stress-strain relationship for the Al-Mg-Li alloy sheet in a wide temperature range within 25-450 degrees C and give an accurate prediction of FLCs under 25 degrees C and 150 degrees C. However, the predicted FLCs are much lower than the experimental ones when the forming temperature is equal or greater than 250 degrees C and the reasons that may cause this great difference are analyzed in detail. (C) 2020 The Authors. Published by Elsevier B.V.