Technological Aspect of Processing Maps for the AA2099 Alloy

Results of an experimental and modelling study of forming processes in the AA2099 Al-Cu-Li alloy, for a wide range of temperatures, strains and strain rates, are presented. The analyses are based on tensile testing at 20 degrees C at a strain rate of 0.02 s(-1) and uniaxial compression testing in the temperature range 400-550 degrees C at strain rates ranging from 0.001 to 100 s(-1), for constant values of true strain of 0.5 and 0.9. The stability of plastic deformation and its relationship with a sensitivity of stress to strain rate are considered. The power dissipation efficiency coefficient, n(%), and the flow instability parameter, xi <= 0, were determined. The complex processing maps for hot working were determined and quantified, including process frames for basic forging processes: conventional forging and for near-superplastic and isothermal conditions. A significant aspect is the convergence of power dissipation when passing through the 500 degrees C peak. Deformation, temperature and strain-rate-dependent microstructures at 500 degrees C for strain rates of 0.1, 1, 10 and 100 s(-1) are described and analysed for the conventional die forging process frame, corresponding to 465-523 degrees C and strain rates of 50-100 s(-1).