Study The Thermal Deformation Identity Under The Influence Of Anisotropic Behaviors Of 7075 Aluminum Alloy Extruded Rods

Hot compression deformation experiment of 7075 aluminum alloy extruded barscolumn sample along the axis direction of 0°, 45°and 90°were carried on the Gleeble-1500thermal simulation machine at temperature of 320℃⁴80℃,at the deformation strain rateof 0.001s^-11s^-1. We got the true stress-strain curve and microstructure at differentconditions by experiment. The constitutive models of high strength aluminum alloy werecreated. Based on the dynamic materials model processing graph theory, processing mapswere drawn and analyzed with microstructure along the different axis direction. The mainconclusions and contents are as follows:1. The main intenerate mechanisms of 7075 aluminum alloy are dynamic recovery anddynamic recrystallization during hot deformation. The peak value stress decreases with thedecrease of strain rate and the increase of deformation temperature. At fixed strain rate, it iseasily given birth to dynamic recrystallization at a higher temperature. And at the sametemperature, it is propitious to dynamic recrystallization at the low strain rate.2. On the condition of low temperature, the stress of 7075 aluminum alloy make agreat difference in the direction of 0°, 45°and 90°.And the stress in the direction of 0°isthe best. On the contrary，when the direction is 45°,it is the worst. With the temperatureincreasing, the stress of 7075 aluminum alloy tends to isotropic and the anisotropy tends tolow.3. Comparing the experimental values to the values of peak stress by the constitutivemodel , the error reached maximal and the value is 18% when the extruded rods axis isalong the direction of 90°, the thermal activation energy along the direction is 145.83KJ / mol. The average error is about 10% when it is along 45 degrees direction and the activationenergy dropped to the minimum value 140.39KJ/mol. The error is the least when it is along0 degrees direction .In low strain rate the value between calculation and experiment is moreconsistent, and the average error at the range of 5%. the values of activation energy alongthe direction 0°reached the maximum 158.45kJ / mol.4. It can be found that the value of power dissipation factor was more bigger when thegrain size was fine. The value was small when the microstructure was uneven. When it wasat a certain direction along the axis and different strain, the thermal processing maps werethe same on the whole. The peak values of power dissipation factor was 0.32 when it wasalong the axis into the direction of 45°and 90. The peak value of power dissipation factorgot 35% when the direction was along the axis of 0°at the deformation temperature rangefrom 460℃to 480℃and strain rate 0.01s^-1to 0.001 s^-1.It was the best area of hotprocessing.From analyzing the influence of microstructure, the shaping processing ability of7075 aluminum alloy extruded bars was very good. The analysis between microstructureand the hot processing maps had the same result. It indicated the result of the hot processingmaps were dependable.In this paper, it build the effective mathematical constitutive equation model for highstrength 7075 aluminum alloy and provided the scientific theoretical groundwork fordetermining hot molding process parameters, improving alloy processing ability andpreventing microstructure defect.