Multi-scale Modeling Simulation And Verification Of Pure Copper Multi-directional Deformation

Pure copper has good plasticity,high density and speed of sound,so it is a key material for making armor-piercing ammunition cover.The microstructure and mechanical properties of the drug-shaped cover play a decisive role in the penetration performance of the jet and the power of the warhead.The multi-directional compression process is widely used for the preparation of fine-grained large-size billets.In this context,this paper has carried out the study of the multi-directional compression deformation behavior of pure copper and the microstructure evolution of heat treatment,established a multi-pass constitutive model for finite element simulation of multi-directional forging and heat treatment processes,used Crystal Plasticity Finite Element Method to predict and analyze the texture evolution of polycrystalline copper compression and realized static recrystallization structure evolution simulation prediction through CA model.First,this paper implements room temperature multi-pass unidirectional compression and heat treatment experiments of pure copper to study the microstructure evolution law under different heat treatment conditions after multi-pass unidirectional compression.Then the effects of temperature,time,cumulative deformation and deformation pass on the evolution of static recrystallization structure are studied through multi-directional forging and heat treatment experiments.The results show that there is an optimal heat treatment temperature and time in the heat treatment process after unidirectional compression and multi-directional forging.There are different optimal heat treatment process parameters with the difference of strain and grain size and the grains are gradually refined with the number of deformation passes increases.The article analyzes the rheological behavior of pure copper multi-pass cold deformation and the evolution of heat treatment structure under different parameters through experiments,and establish the internal variable constitutive structure of pure copper multi-directional cumulative deformation dislocation density based on the dislocation theory and static recrystallization model.Analysis shows that the established model is suitable for multi-pass cold deformation behavior of pure copper.The constructed constitutive was imported into Deform-3D software to explore the effect of heat treatment temperature and time on the static recrystallization behavior of pure copper.The results show that the dislocation density distribution is consistent with the equivalent strain distribution.Recrystallization first occurs in the "X"-shaped large deformation zone composed of the center and four sharp corners,and the center of the end contacting the upper and lower molds has the least degree of recrystallization.Through unidirectional compression and electron backscattering tests,the finite element model of crystal plasticity was established to predict the plastic deformation behavior and texture evolution of materials,and the data transfer between the finite element model of crystal plasticity and the cellular automata was realized.The dislocation density and direction information of the simulation results were input into the static recrystallization CA model as the initial conditions.The evolution of the static recrystallization under different deformation,heat treatment temperature and time was studied,and the microstructure after the second heat treatment was predicted.Finally,combining the microstructure evolution law and the guidance of multi-scale methods on the multi-directional forging process of pure copper,the multi-directional forging and heat treatment experiments are carried out on the large-size pure copper billet.It has been verified that the established process parameters can be used to prepare blanks with fine grains and weak texture strength.