Processing maps and microstructural evolution of isothermal compressed Al-Cu-Li alloy

The hot deformation behavior of an Al-Cu-Li alloy was studied by isothermal compression in the temperature range of 573-773 K with strain rates of 0.01-10 s−1 on a Gleeble-3500 thermo-mechanical simulator. The microstructural evolution during hot deformation was investigated by optical microscope (OM) and transmission electrical microscope (TEM). The results show that the flow stress increases with decreasing deformation temperature and increasing strain rate. Processing maps at the strains of 0.3-0.8 are obtained by isothermal compression data and exhibit two flow instability domains (573-648 K at 0.014-1.5 s−1 and 698-773 K at 0.3-10 s−1) and two peak efficiency domains (723-773 K at 0.01-0.1 s−1 and 573-623 K at 0.01-0.03 s−1). The strain has a significant effect on the peak efficiencies, and the peak efficiencies increase almost linearly as the strain increases. Dynamic recrystallization takes places at high temperatures (673-773 K) and low strain rates (0.01-0.1 s−1). The second phases precipitating dynamically during hot deformation pin dislocations and boundaries of subgrains and restrain the occurrence of dynamic recrystallization, resulting in a higher temperature for dynamic recrystallization. According to the processing maps and microstructural observation, the optimized processing condition of hot deformation for Al-Cu-Li alloy is at 723-773 K and 0.01-0.1 s−1.