Study On Dynamic Recovery And Static Recrystallization Of Al-Cu-Li Alloy

In this paper,the single-pass hot compression test of Al-Cu-Li alloy is carried out,and the flow stress constitutive equation of the alloy and the hot processing map under different strains were established by the true stress-true strain curve,and the thermal deformation softening mechanism was discussed.The hot-rolled sheet of this alloy was cold-rolled with different deformation and annealed.The microstructure evolution of recrystallization annealing was studied by electron backscatter diffraction?EBSD?.The static recrystallization kinetics equations with different deformations were constructed.The conclusions obtained are as follows:?1?During the thermal deformation process of Al-Cu-Li alloy,the flow stress increases rapidly in the initial stage,decreases slightly after reaching the peak value,and then tends to steady state.At high temperature thermal deformation,the stress-strain curve has obvious dynamic recovery characteristics.The constitutive model of Al-Cu-Li alloy under different strain conditions was constructed,and the deformation activation energy is 135 kJ/mol.A dynamic recovery model based on saturation stress is established,in which the saturation stress?_sat,the yield stress?₀,and the dynamic recovery coefficient?can be expressed as a function of the Z parameter.?2?Based on the thermal processing maps with strains of 0.2,0.4,0.6,and 0.8,the optimum process for the hot working of the alloy is the medium temperature and low strain rate zone(deformation temperature is 350-430?,strain rate is 0.01-0.14 s^-1)and strain rate zone at high temperature(deformation temperature is 440-470°C,strain rate is 0.06-0.22 s^-1).The peak efficiency of heat treatment diagram dissipated is between 25%and 28%.The microstructure after hot compression has only a few recrystallization characteristics,indicating that the main softening mechanism of Al-Cu-Li alloy during thermal processing is dynamic recovery.?3?The recrystallization starting temperature of the experimental alloy after 80%cold deformation was 370?,and the recrystallization final temperature was 430?.When the cold deformation is 80%and the annealing time is 430?,the small angle grain boundary changes to a large angle grain boundary,and the average orientation difference angle?changes from 13.6°to 25.2°;when the deformation amount is constant,at different temperatures?370°C⁴30°C?annealing for 30 min,the higher the temperature,the greater the average misorientation?,?increased from 10.5°to25.2°;when the temperature is constant,the deformation is larger,the recrystallization rate is greatly increased,and the recrystallized grains are linearly distributed along the deformation direction.The relationship between the recrystallization rate and the annealing temperature of the alloy accord with the Arrhenius equation.The static recrystallization activation energies of Al-Cu-Li aluminum alloy with cold deformation of 30%,50%and 80%are 320.99 kJ/mol,297.52 kJ/mol and 260.35 kJ/mol respectively.