Study On Microstructure Evolution Of Copper And Its Alloys By Numerical Simulation

Because copper and its alloys have obvious characteristics of good electrical and thermal conductivity,they are widely used in the manufacture of integrated circuit chips and railway contact lines.Practice has shown that the fine crystallization of copper targets can significantly improve the uniformity of the thickness of the sputter deposition,but there are few studies on the grain size process control of the forming process of pure copper sputtering targets.Highstrength copper alloys with high strengthening and conductivity control are generally implemented by cold deformation combined with heat treatment.Fine crystallization is the essence of process control,and there are few related researches on fine crystallization control by hot deformation process.Therefore,it is of great significance to study the influence of hot deformation process of pure copper and its alloys on the microstructure.In this study,TU1 oxygen-free copper and Cu-0.4Cr-0.15Zr-0.04Y high-conductivity copper alloy are used as the object.The method of coupling DEFORM-3D finite element simulation software with cellular automaton technology is used to numerically study the velocity field,temperature field,and stress and strain fields during the reverse thermal extrusion.Based on this situation,the influences of extrusion process parameters such as extrusion temperature and extrusion speed on the recrystallization behavior of copper and its alloys and the microstructure of extrusion are discussed,and the reliability of the simulation results is verified by process experiments..Numerical simulation results of reverse extrusion of pure copper rods show that recrystallization has not generates when the extrusion temperature is in the range of 200?300?,and in the range of 300?800?,as the extrusion temperature increases,the grain sizes of extruded rod substantially present increasing linear.Among them,the stage of 300?450? is an incomplete recrystallization stage.Complete recrystallization generates at the extrusion temperature in the range of 500?550?.The grain size is smaller and the microstructure uniformity is higher.Compared with the process test,the numerical simulation results have good accuracy,and the simulation relative error of the grain size is within±5%.Based on the numerical simulation results of pure copper rod extrusion,a numerical simulation study of reverse extrusion of pure copper tube was carried out.The results show that the grain size changes of the extruded tube is similar to the extrusion rod,but the temperature range of the recrystallization behavior is different.It is an incomplete recrystallization stage at 200?400?,and complete recrystallization stage is at 500?800?.The grain size is smaller and more uniform at 500?,and its average grain size is 24.3?m.When the extrusion temperature exceeds 600?,the recrystallized grains grow significantly;Within the parameters of this study process,increasing the extrusion speed can also increase the recrystallization volume fraction.The numerical simulation results of Cu-0.4Cr-0.15Zr-0.04Y copper alloy reverse extrusion show that the recrystallized grains preferentially nucleate at the grain boundary position;at the same horizontal position,the effective strain and temperature of the tube at edge are higher,thus the recrystallized grains at the edges are finer than the center.At 650?,only partial recrystallization generates at the corners of the mold and the parts in contact with the mold.When the temperature rises to 800?,complete recrystallization generates,and the grain refining effect is the best.Within the scope of the process parameters of this study,the impact of extrusion speed on the recrystallized grain size is small.