Study On The Control And Mechanism Of Microstructure Uniformity Of Cast-rolled 3003 Aluminum Alloy

3003 aluminum alloy is a non heat treatment strengthened aluminum alloy with Mn as the main alloying element.It has been widely used due to its proper strength,good corrosion resistance and weldability.In recent years,roll casting method has been widely used to produce aluminum alloy foil blanks due to its low investment and high efficiency.However,when roll casting method is used to produce aluminum alloy foil blanks,the cooling rate of ingot is fast,the cooling rate of surface and central layer is different,and the diffusion coefficient of Mn element is small.As a result,the Mn element in 3003 aluminum alloy blanks is supersaturated and prone to serious microsegregation,Finally,coarse grain structure and non-uniform structure with large grain size difference are formed in the subsequent heat treatment process of the cold-rolled foil obtained from these blanks,which significantly worsens the formability and mechanical properties of the material.Based on this,this paper mainly discusses the influence mechanism of homogenization process and recrystallization annealing process on the formability and mechanical properties of3003 aluminum foil.The main research contents and conclusions are as follows(1)The influence of homogenization annealing process on the precipitation position,quantity,size and morphology of the second phase particles was analyzed by scanning electron microscopy(SEM)and back scattering electron diffraction(bsed).The results show that the evolution of the second phase during homogenization annealing is mainly controlled by nucleation,growth,Ostwald ripening and heterogeneous precipitation.When homogenization temperature is lower than 500?,precipitation nucleation is the main temperature range;When homogenization temperature is higher than 500?,the main effect is growth and Ostwald ripening;In the low temperature annealing stage of two-stage homogenization treatment,heterogeneous nucleation is dominant.It is also found that when the homogenization temperature is higher than 400?,Al₆Mn needle like precipitation phase with orthorhombic crystal system mainly precipitates in the center of the plate,and a large amount of solid solution Mn element is consumed in the process of precipitation nucleation of this phase,resulting in a precipitation free zone(PFZ zone)near the needle like phase.(2)Through the same cold rolling process and recrystallization annealing at different temperatures,the effects of different homogenization annealing initial structure state and recrystallization annealing process on recrystallization mechanism and precipitation behavior were studied,and the interaction mechanism of second phase precipitation and recrystallization during recrystallization annealing was revealed.The results show that the amount and size of the second phase will affect the recrystallization structure and texture.After annealing at 380?,the original sample,cold rolled sheet pretreated at 400?and 450?have coarse elongated recrystallized grains and strong recrystallization texture,which are affected by the fine precipitates produced during homogenization or recrystallization annealing;The results show that the sheets pretreated at 500?,550?and 600?have fine recrystallization grains and weak recrystallization texture,which is due to the effect of coarse second phase induced nucleation(PSN).There is a simple negative correlation between the density of coarse second phase and the average grain size of recrystallization:y=75.09-30.04x+4.08x².In general,homogenization at 500?can effectively reduce recrystallization texture strength,refine recrystallized grains and basically eliminate plane anisotropy.(3)Based on the different types of recrystallization texture caused by different second phase distribution during homogenization,the formation reason of recrystallization texture was analyzed.The results show that the recrystallized annealed microstructure mainly contains M,P and cube oriented grains,and the distribution of M,P and cube oriented grains in the surface and center is not the same.The M-oriented grains are mostly distributed in the center,while the P and cube oriented grains are mostly distributed in the surface.After single-stage annealing at600?,Cube and Cube-ND have the advantage of nucleation size,which leads to faster growth rate in two-stage annealing,and finally obtain larger grain size and stronger Cube and Cube-ND recrystallization texture.M and P do not have the advantage of nucleation size in the nucleation stage.After the final two-stage annealing,M and P grains are gradually engulfed by other oriented grains,resulting in the weakening of M and P oriented recrystallization texture.