Abstract:A new Al-Zn-Mg-Cu high strength aluminum alloy after solution and aging pre-treatments of 435 oC/2 h+200 oC/12 h was taken as the object and hot compressions at temperatures in the range of 350~400 oC, strain rates in the range of 0.01 to 1 s-1 and height reduction up to 60%~80% were carried out followed by subsequent annealing and solution treatments of 350 oC/0.5 h+470 oC/2 h. The influences of precipitated particles on grain evolution mechanisms and regulations during hot deformation and subsequent annealing and solution treatments were investigated by optical microscope (OM) and electronic microscope (EBSD, TEM). The conclusions can be drawn as following. (i) Continuous dynamic recrystallization occurs under deformation conditions of 400 ℃, 0.05 s-1, 60%, the value of lnZ is 24.33, and refined and uniform recrystallized grains appear. After subsequent annealing and solution treatments, recrystallized grains become more equiaxed and uniform, and the size of grains increases slightly. As a result, the refined, equiaxed and uniformly-distributed grain structure occurs. (ii) When hot compression is carried out under conditions of 380 oC, 0.1 s-1, 60%, the value of lnZ increases to 25 or so, grains are elongated along the deformation direction with some refined recrystallized grains at the grain-boundaries. After subsequent annealing and solution treatments, grain growth is not too much, and refined and recovered well sub-grains come forth evenly in the elongated grains. As a result, the elongated grain structure with refined and uniform sub-grains emerges. (iii) At other conditions of increased strain rates or decreased temperatures, the value of lnZ increases to about 26, and deformation increases to large values, dynamic recrystallization can not be observed obviously and the prior grains are elongated severely. After subsequent annealing and solution treatments, the grains grow rapidly. As a result, the coarse grain structure appears