Study On Thermal Deformation Behavior Of Rapid Cooling 7055 Aluminum Alloy

The composition of 7055 aluminum alloy contains Trace elements of Zn,Cu and Mg.It is a new type of aluminum alloy developed after changing the alloy composition based on 7050 alloy.The metal deformation behavior and metallographic evolution at 250?-450?,0.001 s^-1-10s^-1temperature and strain rate were studied.The alloy rheological characteristics and microstructure were combined with the processing map to analyze the structure evolution mechanism of the alloy in different processing intervals,so as to control the influence of processing parameters on the structure.On this basis,the forging forming simulation was carried out for 7055aluminum alloy,and the analysis was combined with the microstructure.The main conclusions are as follows:After the thermal simulation compression test,the processability of 7055aluminum alloy was studied.Based on the real stress and strain data obtained from the experiment,four constitutive relationship models were established,namely AR constitutive model,M-JC constitutive model,M-ZA constitutive model and ANN constitutive model,and evaluated the accuracy of these models.M-ZA model has good predictive ability under low temperature and low strain rate conditions;AR model has good predictive ability under lower deformation temperature;while M-ZA model can predict intermediate temperature and lower The flow stress curve under the condition of strain rate;in comparison,In contrast,ANN model is more reasonable than other models.On the basis of the experiment,the metallographic changes of 7055 aluminum alloy during machining were studied and the machining diagram was established by combining with a certain instability condition.The results show that when the strain rate is 0.001s^-1,the original elongated grain structure is gradually replaced by dynamic recrystallization,and the newly formed recrystallized grains are fine and uniform;when the temperature is 450?,the increase of strain rate will lead to the gradual disappearance of grain growth.When the temperature is 350?,the main mechanism of microstructure evolution is dynamic recovery,and the main mechanism of dislocation evolution is the formation of small-angle grain boundaries and subcrystals by dislocations.When the strain rate is 0.1s^-1,as the temperature increases,the grain evolution mechanism of the microstructure gradually changes from dynamic recovery to dynamic recrystallization.When the temperature is 350°C-400°C and the strain rate is 0.01s^-1-0.1s^-1,not only the power dissipation efficiency is the highest,but there is no instability zone.On this basis,the thermal simulation forming process of 7055 aluminum alloy was simulated.According to the results,When the deformation temperature is 250?,the optimal forging speed is 120mm/s.The maximum equivalent strain area of forging is smaller than other deformation velocities and distributed near the discharge hole.After punching,the distribution area of low damage value is more and the average damage value is lower.When the deformation velocity was 12mm/s,the optimal forging temperature was 400?,the area with the highest damage value after punching was small,and the damage distribution was uniform in the burr area.