Hot deformation behavior and microstructure characteristic of 2055 Al-Li alloy during uniaxial compression

Abstract

The hot deformation behavior of as-extruded 2055 Al-Li alloy at T6 state has been investigated by uniaxial hot compression test in a Gleeble-3800 thermal simulation machine at the temperature of 320 ^o C, 380 ^o C, 440 ^o C, 500 ^o C with strain rate ranging from 0.001 s ^−1 to 1 s ^−1 . Deformation instability occurred under the deformation condition of 380 ^o C/5 s ^−1 and at the deformation temperature of 500 ^o C via the shape of flow curve and the side view observation of the compressed samples. The serration in flow curve of the low strain rate suggests occurring of DSA. The constitutive equation based on Arrhenius equation were established with the deformation activation energy of 174.6 kJ mol ^−1 . The microstructures of the compressed samples were analyzed by OM and TEM, the DRXed grains could be observed in the compressed samples at 440 ^o C with strain rate of 1 s ^−1 and 0.001 s ^−1 . The dominated precipitates in the alloy were plate-shaped T _1 phase and spherical β _1 phase. The precipitates-dislocations interaction was analyzed by HRTEM. The dislocations could be pinned by both the T _1 phase and β _1 phase, and the precipitates and dislocations around them divided the grain into small zones, and the misorientation across the dislocation was about 0.8 ^o .

Keywords

• Al-Li alloy
• deformation behavior
• microstructure
• activation energy
• precipitates
• DRV