Abstract:The Al-4.10Cu-1.42Mg-0.57Mn-0.12Zr alloy was compressed to different strains at deformation temperature of 300 oC and strain rate of 10 s^-1 on Gleeble-1500 system. The dynamic complex microstructures evolutions were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The true stress-true strain curves exhibited a peak stress at critical strain, after which the flow stresses decreased monotonically, showing a dynamic flow softening. As the strain increased, the dislocation tangled to cell structure and sub-grain structure, which indicated the occurrence of dynamic recovery during deformation. Dynamic precipitations of S (Al₂CuMg), θ (Al₂Cu) and Al₃Zr phase were accelerated and coarsened by deformation. Continuous S phases precipitated in the Al matrix and discontinuous S phases were found to be nucleated near the Al₃Zr phase and at the sub-grain boundary. The flow softening mechanism was resulted from the reduction of dislocation density which attributed to dynamic recovery and precipitates coarsening.

Key words: aluminum alloy; hot deformation; flow softening; dynamic recovery; dynamic precipitation