The effect of annealing temperature on the recrystallization and mechanical properties of severe plastic deformed commercial pure aluminium during ultra-fast annealing

Abstract

Abstract In the research a commercial pure aluminium was cold rolled by 98% accumulative severe plastic deformation and then ultra-fast annealed at 350 °C−520 °C with the 1000 °C/s heating rate and 1.0 s holding time. The microstructure evolution and the mechanisms of the recovery and recrystallization for the above ultra-fast annealed pure aluminium were analyzed by Gleeble 3500 thermal simulation system, electron backscatter diffraction(EBSD),and transmission electron microscopy (TEM). For the ultra-fast annealing pure aluminum, the grain size increases from 2.05 μm to 17.10 μm with the increase of annealing temperature from 410 °C to 520 °C; the tensile strength of the annealed pure aluminium decreases from 116.48 MPa to 53.43 MPa, and the uniform elongation increases from 1.20% to 39.78%. When annealing at 410 °C, the storage energy was transformed into the driving force for grain nucleation, which greatly refined the grains. When annealing at 380 °C ∼ 410 °C, the pure aluminium is in the stage of recrystallization, and the average grain size refined to 2.05 μm. When annealing at 435 °C, the number of small-angle grain boundaries (<15°) was significantly reduced and the number of large-angle grain boundaries increased. When the annealing temperature increased to 470 °C or 520 °C, the crystalline grains had merged each other, leading to the grain size grow to 17.10 μm. The annealing temperature of ultra-fast annealing should be in the range of 410 °C to 435 °C for optimizing the mechanical performances of commercial pure aluminum.