| 7075 aluminum alloy has the characteristics of low density,high specific strength and specific stiffness,making it widely used in industries such as aerospace,high-speed rail and automobile industries.As a new type of plasticizing forming technology,electric impact-assisted forming can effectively improve the room temperature forming properties of 7075 high-strength aluminum alloy.However,the electroshock assisted forming process involves the synchronous coupling of electrical,thermal and mechanical fields,and the dynamic evolution mechanism of the deformation structure is very complicated.In this paper,a cellular automata model for the evolution of microstructure recrystallization based on the electroshock assisted tensile deformation was established,the evolution law of dynamic recrystallization of7075 aluminum alloy during the electroshock assisted forming process was predicted,and the effect of electroshock parameters on the microstructure was revealed.The influence mechanism has important reference significance for realizing high-performance manufacturing of high-strength aluminum alloy components.The main research elements of this paper are as follows:Firstly,based on the characteristics of microstructure evolution during low frequency electroshock assisted forming,the framework and basic settings of the cellular automata model are determined,the grain growth form is determined,and the initial structure is calculated and generated.Coupled electroshock energy to model the dynamic recrystallization of 7075 aluminum alloys under combined electrical-thermal-force fields.A real stress-strain curve was obtained by thermal simulation of unidirectional tensile tests to establish an intrinsic model for describing the rheological stress of 7075 aluminum alloy and to determine the parameters of the cellular automata model.Secondly,the simulation results under different electroshock parameters are experimentally verified,and the relative error between simulation and experiment is within±5.21%,which proves the accuracy of the model.Based on the cellular automata simulation results,it is found that with the increase of current density and electroshock period,the area fraction of dynamic recrystallization first increases and then decreases,and the average grain size shows the opposite trend.Under the optimal parameters with the highest dynamic recrystallization ratio,that is,when the current density is 30 A·mm-2and the electroshock period is 5 s,a microscopic morphology with fine and uniform grain distribution can be obtained.The average grain size at this time is only 14.78μm,which is 31.83%smaller than that of the non-electric tensile specimen.Finally,the results of the electroshock assisted tensile mechanical properties tests were analyzed and the highest elongation of 13.33%was found for the optimal electroshock parameters,which is 21.74%higher than that of the non-electric tensile sample.The effects of electroshock on dislocations,recrystallization nucleation and growth were analyzed from the perspective of physical modeling,and it was found that electroshock effect promote the movement of dislocations and recrystallization nucleation,while excessive current density inhibits the growth of recrystallization.From the microscopic characterization results,it was found that the electroshock effect significantly reduced the precipitate size and induced the migration of intragranular dislocations to the grain boundaries,which enhanced the dynamic recrystallization behavior of 7075 aluminum alloy. |
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