Microstructure evolution and precipitates growth/dissolution behavior of 7050 aluminum alloys during high-temperature tension

Dynamic recrystallization (DRX) is one of the convenient and effective grain refinement mechanisms during hot deformation, and it is closely related to the precipitation behavior. High temperature tensile tests of 7050 aluminum alloy with a temperature range of 553-713 K and a strain rate range of 0.001-0.1 s-1 were carried out using a thermomechanical machine. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were employed to characterize the evolution of the microstructure and the growth/dissolution behavior of the precipitates. The results show that the deformation temperature and strain rate had a significant effect on the softening mechanism and precipitation behavior, and dynamic recovery (DRV) occurred throughout the test temperature range. Discontinuous dynamic recrystallization (DDRX) was observed at 633 K with a strain rate of 0.001 s-1 and 0.01 s-1. DDRX and Continuous dynamic recrystallization (CDRX) occurred simultaneously at temperatures of 673 K and above. The Mg(Zn, Cu, Al)2 phase (eta) experienced the growth followed by re- dissolution as the deformation temperature increased, with their number decreasing and their size increasing first and then decreasing. The Al2CuMg phase (S) grew along the [010]Al and [001]Al directions, and the rapid diffusion of solute atoms through dislocation channels facilitated by dislocation-induced precipitation, results in an unusually coarse of them.