Research On Hot Deformation Behaviors And Microstructure Evolution Of Pure Copper

Pure copper is the key material for the manufacture of high-explosive anti-tank conic liner due to its high density and sound speed,good plasticity and excellent comprehensive performance.The microstructure and mechanical properties of the conic liner have a decisive influence on the penetration performance and warhead damage power of the formed jet or projectile.Thermoplastic machining is a key process in the manufacture of high penetration conic liner,which has a significant impact on the mechanical properties of the components.Therefore,To study the hot deformation behavior and microstructure evolution of pure copper and establish the internal relationship between the flow behavior and microstructure of the material is of great significant to realize the cooperative control of formation and property.In this paper,constitutive models,microstructure simulation and processing map are used to systematically study the hot deformation behavior and microstructure evolution of pure copper,which provides theoretical support for the optimization of thermal processing process of pure copper.The main research work and results is as follows:The deformation behavior and microstructure evolution of copper at temperatures of 500?800?and strain rates of 0.001?1s^-1 is studied by the isothermal compression test.Based on dislocation theory,the DRV-DRX piecewise constitutive model and the unified dislocation density based model were established.The error analysis shows that the two models are suitable for hot temperature deformation behavior description of pure copper.The piecewise DRV-DRX constitutive model with few material parameters has high computational efficiency.The unified dislocation density based constitutive model establishes the internal relationship between flow stress and microstructure evolution,which can be applied to the prediction of flow stress under complex deformation conditions.The established DRV-DRX piecewise constitutive model were introduced into the DEFORM software material library for copper sample hot compressive deformation simulation.The finite element simulation results were input to dynamic recrystallization CA model as the initial condition for the simulation of recrystallized grain size evolution in different deformation zone.The average error and maximum error of simulated recrystallized grain size and the actual grain size are 9.25%and 17.7%respectively.The results show that the established dynamic recrystallization model has higher prediction accuracy.It can be found that the dynamic recrystallization degree in easy deformation zone is larger than difficult and free deformation zone.And higher temperature and lower strain rate can promote dynamic recrystallization nucleation and grain growth.The average grain size of recrystallized microstructure under high temperature and strain rate is8?12?m.The recrystallized grain sharply grew up to 60?m under high temperature and low strain rate.The processing map of copper was constructed based on dynamic material model and plastic instability criterion.Combined with processing map and microstructure analysis,the hot-workability of copper in stable regions and unstable regions was analyzed.It can be found that the plastic instability area mainly appeared in low temperature and high strain rate.And the hot deformation condition of pure copper was optimized as 700?800?,0.1?1s^-1.