Effect Of Zr On Microstructure And Properties Of 5083 Aluminum Alloy Cast Rolled Plate

5083 aluminum alloy is a non heat treatable aluminum alloy,which has excellent corrosion resistance,weldability and medium strength.Twin roll casting is a production method that the molten metal is solidified by water-cooled rolls and rolled into plates,it has many advantages,such as small area of casting and rolling mill,centralized equipment distribution,low energy consumption and low cost,however,the casting and rolling process is relatively short,the metal melt undergoes two processes of casting and rolling in a very short time,which leads to the complex heat conduction direction and metal deformation mode during casting and rolling,therefore,cracks,coarse phases and centerline segregation are easy to occur in the production process of plates.Therefore,the subject plans to improve the structure and comprehensive properties of 5083 aluminum alloy cast rolling plate by adding trace Zr element.The casting and rolling experiment was carried out on NF6-300 vertical twin roll strip caster,with the pouring temperature of 680℃,roll speed of 12 m/min,and roll gap width of 2 mm,finally,four 5083 aluminum alloy cast rolling plates with different Zr content are obtained,then,different Zr content 5083 aluminum alloy cast rolled plates were homogenized at 470℃for different times.Optical microscope and scanning electron microscope were used to observe and analyze the structure of the edge and center of the cast rolling plate,and the hardness,tensile property and corrosion resistance were tested,the microstructure and properties of 5083 aluminum alloy cast rolled plates with different Zr content in as cast and homogenized annealing were studied,the main existing forms and action mechanism of Zr in 5083 aluminum alloy cast rolling plates in different states are analyzed.（1）Zr has obvious refining effect on the grain of 5083 aluminum alloy cast rolling plate,mainly because the primary Al₃Zr phase can be used as the core of heterogeneous nucleation,so that the grain can be significantly refined.Zr can reduce the solid solubility of other solute elements in aluminum base,with the increase of Zr content,the precipitates on the grain boundary at the edge obviously increase,so that the mechanical properties of the cast rolling plate are improved,and the coarse eutectic phase at the center is improved.When Zr content is 0.25%,the comprehensive properties of the cast rolling plate are the best,at this time,the shape is better,tensile strength,yield strength,elongation,hardness of the edge and center are137.12 MPa,98.37 MPa,10.21%,91.32 HV0.1 and77.91 HV0.1 respectively.（2）The original cast rolled sheet was homogenized at 470℃for 6h,10h and 14h respectively.It is found that with the prolongation of homogenization annealing time,the microstructure of the edge and the center tends to be uniform,and the grains gradually grow up to 85.3μm,the Al₃Mg₂phase on the grain boundary at the edge and the coarse eutectic phase at the center gradually dissolve,the hardness,tensile strength and compressive strength are gradually reduced,and the elongation is increased.（3）The 0.25wt.%Zr cast rolled sheets were homogenized at 470℃for 6h,10h and 14h respectively.It is found that with the extension of homogenization time,there are rod like Al₃Zr phases in the edge and center,Al₃Zr interposition on grain boundary can inhibit recrystallization,grains gradually grow up to 71.8μm,hardness and strength decreased gradually,and the elongation increased.