The Interaction Of Precipitation And Recrystallization During Annealing In AA3003Cast-rolling Aluminium Alloy

AA3003aluminium alloy contains the major alloying element Mn, which is non-heat-treatable. As the cooling speed of ingot casting is faster and the diffusion coefficient of Mn element is small, the matrix segregation is very serious in the cast-rolling production, which leads to coarse grains in the intermediate annealing. Refining the grains is the focus of this study, and the recrystallization is an important means of improving grain structure. This study concerns the widely used AA3003cast-rolling aluminium alloy as the experimental material. The effects of cold rolling deformation and annealing process on the recrystallization grain structure were investigated by means of electrical conductivity measurements, hardness, polarized light microscopy, scanning electron microscopy and transmission electron microscopy.(1) In order to shorten the production process and reduce the energy consumption of the industrial production, the precipitation behavior of AA3003aluminium alloy was controlled precisely to achieve the fine grain structure by cold rolling deformation and intermediate annealing without homogenization. The results show that the temperature of the precipitation peak is decreased obviously and a double peak is observed as the reduction increases during the isothermal annealing; Due to the moving precipitation peaks and the effect of recrystallization, the precipitation behavior of AA3003aluminium alloy is complicated. The annealing temperature can change the interaction of precipitation and recrystallization; and the segregation of AA3003aluminium alloy cast-rolling plate is very serious, and the recrystallization apparent activation energy(Q71%=208.2KJ/mol) is too higher to achieve the desired effect.(2) According to the serious segregation of AA3003aluminium alloy cast-rolling plate, the effective homogenization reduces the Mn segregation and improves the uniformity of matrix. The density of bulky second phase particles in the matrix is improved during homogenization, and refine the grains by PSN during the intermediate annealing. The results show that the cold rolling deformation obviously promotes recrystallization, the reduction increases from40%â†'70%â†'85%, and the activation energy from155.2kJ/molâ†'128kJ/molâ†'110kJ/mol respectively; Increasing the annealing temperature and the cold rolling deformation can obviously reduce the recrystallized grain size(150μmâ†'35μm). The recrystallization prior to the precipitation is completed during the annealing at high temperature, and then the precipitation inhibits the recrystallized grains from growing up. In the same way, the completion of recrystallization offers many precipitation nucleation positions, such as grain boundary, which promotes the precipitation.