Abstract:GLEEBLE-3500 thermal simulation system and EBSD technology were used to study the microstructure evolution of 5083 aluminum alloy under ultra-fast annealing. The effects of rapid heating rate, annealing temperature and cold rolling deformation on the grain size of 5083 aluminum alloy were discussed. The average grain size of 5083 aluminum alloy was refined from 7.43 μm to 4.98 μm with the increase of the heating rate from 25 ℃/s to 500 ℃/s. After ultra-fast annealing (heating rate 500 ℃ / s, holding time 3 s, cooling rate 40 ℃ / s) at different annealing temperatures (350 ℃, 400 ℃, 420 ℃, 450 ℃ and 500 ℃), the grain size of the 80% cold-rolled 5083 aluminum alloy first decreased and then increased. When annealed at 420 ℃, the minimum grain size was 4.82 μm. The grain size of recrystallization was affected by the interaction of boundary migration rate and nucleation rate. During the ultra-fast annealing at 350 ℃ ~ 420 ℃, the nucleation rate increased sharply due to the rapid heating, while the nucleation temperature was low, which makes the grain boundary migration rate smaller, resulting in the grain boundary migration rate less than the nucleation rate, and the recrystallization grain size was refined from 5.23 μm to 4.82 μm; During the ultra-fast annealing at 420 ℃ ~ 500 ℃, the nucleation temperature became higher and the grain boundary migration rate increased rapidly. The grain boundary migration rate was higher than the nucleation rate, which makes the grain coarsening from 4.82 μm to 6.20 μm. 420 ℃ was a critical point for the competition between the grain boundary migration rate and the nucleation rate of 5083 aluminum alloy. After 50%, 60%, 71.4%, 80% and 87.5% cold rolling, 5083 aluminum alloy was heated to 450 ℃ for 3 s at an ultra-rapid heating rate of 500 ℃ / s and cooled at 40 ℃ / s. The average grain sizes were 7.94 μ m, 6.82 μ m, 6.03 μ m, 4.98 μ m and 4.84 μ m, respectively. With the increase of rolling deformation, the grain size decreased, but after the cold rolling reached 80%, the grain size decreased unobviously.