Hot deformation behavior and microstructural evolution of homogenized 7050 aluminum alloy during compression at elevated temperature

Abstract

Hot compression tests of homogenized 7050 aluminum alloy were carried out on the Gleeble-1500 thermal simulation machine, and the associated microstructure was studied using electron back scattered diffraction technique and transmission electron microscopy. The results showed that the peak stress levels decreased with the increase of deformation temperatures or the decrease of strain rates, which can be represented by the Zener–Hollomon parameter in the exponent-type equation with the hot deformation activation energy of 160.3kJ/mol. With the decrease of Z values, results showed a continuous decrease in very low angle boundaries, exhibiting a misorientation between 2° and 5°, associated to substructure, and a steady increase in the other higher angle boundaries, especially with the misorientation angles between 30° and 60°. And such an evolution is due to the increase of subgrain size with the decrease of Z values. At lower Z, the dislocations collected into more widely spaced and less dense tangles. As strain rose, the tangles reorganized into subgrains with walls that were more widely spaced and straighter; they had fewer, more regularly arranged dislocations. The main softening mechanism of homogenized 7050 aluminum alloy is dynamic recovery.