Study On The Second Phase And Properties Of Cast-Rolled AA8111 Aluminum Foil Blank For Aseptic Packaging

AA8111 double0zero aluminum foil is an important foil for aseptic packaging brands such as Tetra Pak and Combibloc,which has excellent mechanical properties and surface quality,and the production of aluminum foil blanks is mainly used Hot-rolling process in the international currently.The aluminum foil blank produced by the Cast-rolling has the advantages of low energy consumption and short production process,but there is a problem that the pinhole ratio of the finished aluminum foil is high when the Hot-rolled AA8111 alloy composition is directly used.By adjusting the composition of Fe and Si,a kind of AA8111 aluminum alloy suitable for casting and rolling production was developed,which provided theoretical guidance for the production of cast-rolled AA8111 blank in this paper.In this paper,Optical Microscope(OM),Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS),X-ray Diffraction(XRD),Differential Scanning Calorimeter(DSC),mechanical properties and forming properties tests and double zero aluminum foil second phase extraction were used to study the second phase and performance change law of Cast-rolled AA8111 aluminum foil blank during cold deformation.Furthermore,the formation process and mechanism of pinholes during aluminum foil rolling were explored.Research indicates:The second phase of the surface layer in the adjusted cast-rolled sheet structure was mainly granular,but the distribution of the coarse-grained(a-AlFeSi)and strip-like(?-AIFeSi)second phase in the central layer was significantly reduced compared with that before adjustment and there no precipitation of free Si phase was observed locally.After homogenization annealing at 550?×21h,the coarse second phases in the 4.1mm plate structure dissolved basically,some Fe,Si supersaturated solid solution decomposed,the granular phase distribution increased,and the rod-shaped Si phase precipitate which were 5?m in the structure.The coarse?-AlFeSi phases which not completely dissolved further refined into a thin strip simultaneously.Furthermore,the distribution of the annealed precipitated rod-like Si phase and the thin strip phase ?-AlFeSi phase were significantly reduced compared with that before the adjustment,and the aluminum foil second phase extraction experiment further confirmed that the strip ?-AlFeSi phases wereAlsFeSi and Al3FeSi.When the adjusted billet was cold-rolled to 0.24mm,the distribution of the second phase larger than 5?m in the microstructure was about 5.17%,which significantly lower than the 8.8%before adjustment and there was no phenomenon that the large granular second phase aggregates and linear distribution.When the foil was further rolled to 0.015 mm,the distribution of the large-sized second phase in the tissue was reduced and the distribution of the second phase was more uniform.The rod-shaped Si phase precipitated during homogenization annealing was crushed into large particles,which retained the aggregate distribution during cold deformation of the structure.The refinement of the large-size ?-AlFeSi phase reduced in size,but it also retained the characteristics of the tip and large aspect ratio.They all showed strong tissue heritability and increased the number of immutable hard spots in the tissue,which increased the inconsistency of tissue deformation and local stress concentration of tissue.When the aluminum foil was rolled to a certain thickness,part of the large-size p-AlFeSi phases and the large-grain hard phases begin to slide under the action of the roll and separate from the matrix structureand fall off to form pinholes,which partially led to a continuity and narrow linear splitting pit on the surface of aluminum foil.The difference in the distribution of Si phase and ?-AlFeSi phase in the microstructure was the main reason for the difference in the quality of the aluminum foil before and after the adjustment and it was also an important reason for the pinhole of the cast AA8111 aluminum foil.The tensile strength and elongation of the adjusted blank changed more linearly and the dimple deformation and tearing ridges appearance lag one pass than before adjustment.When rolled to 0.24mm,the tensile strength of the blank in the three directions of 0?,45oand 900 were close to that before the adjustment,but the elongation were 3.1%,9.6%and 14.3%higher respectively.At the same time,the dimples were relatively dense and deep.In addition,the adjusted finished blank had a cup diameter of 4.84,which was 4.5%higher than the 4.63 before adjustment and which had better plasticity and formability.With the reduction of the thickness of the double-zero aluminum foil,the number of pinholes were greatly increased.When the aluminum foil changed from 5.85?m to 5.36 ?m,the pinhole ratio after adjustment was only increased by 120/m2,which was much lower than the 420/m2 before the adjustment.The pinhole ratio of 5.36?m foil after adjustment was nearly doubled compared with before adjustment,and the breakage rate and yield were also improved.The adjusted billet was more conducive to rolling thinner aluminum foil,which has been used in actual production.