Hot deformation characterization of as-homogenized Al-Cu-Li X2A66 alloy through processing maps and microstructural evolution

Abstract

Uniaxial compression tests were carried out on an Al-Cu-Li alloy at a temperature range of 300–500°C and a strain rate range of 0.001–10 s−1. Four representative instability maps based on Gegel, Alexander-Malas (A-M), Kumar-Prasad (K-P) and Murty-Rao (M-R) criteria were constructed. Through formula deduction and microstructural observation, it can be concluded that M-R criterion is more accurate than K-P criterion, and the first two criteria are better than Gegel and A-M criteria. From a power dissipation map and a M-R instability map, the optimized processing parameters are 480–500°C/0.001–0.1 s−1 and 420–480°C/0.1-1 s−1. The corresponding microstructural analysis shows that dynamic recovery and partial dynamic recrystallization are main dynamic softening mechanisms. Transmission electron microscopy observation indicated that a large number of primary coarse T1 (Al2CuLi) particles precipitated in the homogenized specimen. After deformation at 500°C, most of the primary T1 particles dissolved back into the matrix, and secondary fine T1 particles precipitated at deformation-induced dislocations, high angle grain boundaries and other dispersed particles.