Effect of temperature and strain rate on hot deformation behavior and microstructure of Al-Cu-Li alloy

Al-Cu-Li alloy (AA2195) was produced using vacuum induction melting (VIM) furnace under dynamic argon atmosphere. The as-cast billets were homogenized using a two-step homogenization cycle. The hot deformation behavior of homogenized and forged AA2195 alloy was studied by hot isothermal compression in a thermo-mechanical simulator. The contour maps of efficiency of power dissipation and instability maps have been generated within the temperature range of 250-450 °C and strain rate range of 10−3-102 s−1. Various deformation mechanisms, which operate in different temperature-strain rate regimes, were identified with the aid of these maps and complementary microstructural analysis of the deformed specimens was carried out. Results indicate four distinct deformation domains within the range of experimental conditions examined. Out of these four domains, the optimum temperature and strain rate range for obtaining a completely reconstituted microstructure is T: 400 °C-450 °C andε˙: 10−2-10−1.5 s−1 andε˙: 10−0.5-101 s−1. Instability mechanisms in the material are attributed to localized plastic flow and cracking. A constitutive equation that describes the flow stress of AA2195 alloy as a function of strain rate and deformation temperature was also established.