Dynamic microstructural evolution of Al-Cu-Li alloys during hot deformation

Abstract

In this work, we investigated the evolution of deformation microstructures and multiscale phases of Al-Cu-Li alloy under different temperatures and strain rates. The results clearly show that the compress temperature affects the characteristic and dynamic deformation behaviors of secondary phases in Al-Cu-Li alloy during the hot deformation process. The fragmentation and dissolution occur on initial coarse Al2CuLi(T1) phases through the shear defromation of T1 phase at 340 °C and 420 °C. Dislocations and low angle grain boundaries (LAGBs) produced by the compressive deformation can provide a large number of sites for the heterogeneous nucleation of secondary T1 phase precipitates. We observed that the secondary T1 precipitates form a multistage band structure, composed of several fine and thick T1 phase precipitates arranged in parallel with a certain angle. Under the deformation temperature of 420 °C, the strain rates can accelerate the formation of T1 precipitates which exhibit diversified morphologies. However, the T1 precipitates dissolve into the matrix absolutely when the deformation temperature reaches 500 °C. The proper strain rates (0.01–1 s−1) can promote the precipitations and the growth of multistage banded T1 phase. Moreover, the β'(Al3Zr) and Al20Cu2Mn3 phases in the alloy are stable during the thermal deformation process.