Experimental Study On Mechanical Properties Of 6082-T6 Aluminum Alloy Under Temperature-Strain Rate Coupling

6082 aluminum alloy is an alloy,which has excellent properties such as high strength,easy processing and strong corrosion resistance.Under the premise of not losing the extrusion performance of profiles,its corrosion resistance and weldability are superior to other aluminum alloys.In the service environment,aluminum alloy structures are often affected by single or combined effects of many factors,such as static load,dynamic load,high temperature,impact and corrosion.At present,there are many studies on the mechanical behavior of 6082-T6 aluminum alloy under the single condition of conventional static load,dynamic load and temperature,but there are few studies on the mechanical behavior under the condition of simultaneous coupling of the two,and no related model has been put forward.Therefore,this paper will carry out tensile,compressive and impact tests on 6082-T6 aluminum alloy under the control of temperature and strain rate,establish a traditional constitutive model,and optimize it on the basis of the traditional model.At the same time,the critical condition of dynamic recrystallization of this material is analyzed,and the thermal creep model and the dynamic equation for predicting the dynamic recrystallization volume fraction are established,which provides reference for the processing technology of aluminum alloy.(1)At room temperature,quasi-static tensile and compressive tests were carried out on6082-T6 aluminum alloy by electronic universal testing machine,and the basic mechanical properties of the material were obtained.The experimental results show that the material shows obvious brittle fracture in the quasi-static tensile process.The experimental data and the calculation method of strain hardening coefficient of constitutive model are analyzed and studied.A method to solve the hardening index of aluminum alloy materials based on platform compiled genetic algorithm(Genetic algorithm,Ga)is proposed.And simulation verification is carried out based on the Abaqus platform.The results show that 6082-T6 aluminum alloy has good tensile strength and ductility.Compared with the traditional method,the genetic algorithm(Ga)is more stable in solving the hardening index.The real stress-strain curve and simulation results verify the correctness of the optimized constitutive model,which can be used to predict the mechanical properties of aluminum alloy materials.(2)Taking high strain rate and temperature as the main influencing factors,the high-temperature dynamic compression test of 6082-T6 aluminum alloy was carried out by Hopkinson pressure bar device with synchronous assembly heating system,and the real stress-strain curves at different strain rates and heating temperatures were obtained.The rheological constitutive model and the effects of strain rate and heating temperature on the mechanical properties of the material were emphatically analyzed.The results show that under dynamic impact load,the elastic modulus of the material is negatively correlated with strain rate and negatively correlated with temperature.According to the theory of thermally activated dislocation,in the range of experimental strain rate,with the increase of strain rate,the yield stress of the material increases obviously,showing obvious strain rate strengthening effect.At high temperature,with the increase of temperature,the flow stress of the material decreases,resulting in the reduction of yield strength.The material shows a strong temperature softening effect,and the internal thermal softening effect of the material has the upper hand in the competition with work hardening(strain hardening).Therefore,compared with the strain rate strengthening effect,the temperature softening effect has a more significant effect on the mechanical properties of materials.At the same time,the impact failure mechanism of materials was analyzed by metallographic microscope and scanning electron microscope,and J-C constitutive model was introduced.The strain rate strengthening term and temperature softening term in the model were modified differently.Considering the influence of absolute temperature rise,the optimized rheological stress-strain constitutive model of materials was obtained,which provided corresponding parameters for the impact simulation of materials.(3)Taking low strain rate and temperature as the main influencing factors,the hot compression creep experiment of 6082-T6 aluminum alloy sample was carried out by Gleeble-3500 hot compression simulation compressor,and its creep behavior was studied by scanning electron microscope.The results show that deformation temperature and strain rate are important factors affecting dynamic recrystallization.Reducing temperature and increasing strain rate will weaken dynamic recrystallization,and DRX critical condition and peak stress(strain)will increase.The constitutive equation of hot creep of 6082 aluminum alloy was established by introducing the work hardening rate-rheological stress curve,and the relationship between DRX critical condition,peak stress(strain)and parameter Z during creep was explored.Based on Avrami equation,the prediction equation of DRX volume fraction is established.With the increase of strain,DRX volume fraction is characterized by slow increase,then rapid increase and then slow increase.In the hot forming extrusion process of 6082 aluminum alloy,according to the volume fraction prediction equation,the DRX can be reduced and the internal structure of the material can be optimized by changing the extrusion conditions and particle size.