Numerical Simulation And Experimental Verification Of Sheet Rolling Process Of W-Cu20 Powders

Tungsten copper alloy sheet has high strength,hardness and low thermal expansion coefficient,as well as good electronic conductivity and thermal conductivity.It has been widely used in electric contacts,electronic packaging materials and heat sink materials.Because the melting point of tungsten is much higher than copper and they are not solid solution,the traditional method of rolling ingots is not suitable for the preparation of tungsten copper alloy sheets.It is an excellent way to prepare tungsten copper powders alloy by using powder rolling technology and subsequent sintering process.And powder rolling process has many advantages,such as the production of plate composition and tissue is uniformity,equipment is simple and low costs.In this paper,the rolling law of W-Cu20 powders was studied by the way of combining finite element numerical simulation and practical tests.With tungsten powder and copper powders as the raw materials,the Drucker-Prager/Cap model of W-Cu20 powders was constructed.And a finite element simulation model of W-Cu20 powder rolling was established subsequently.By comparing the simulation results with the actual tests,it was considered that the numerical simulation of W-Cu20 powder rolling in this paper was credible.According to the simulation results,the influence of process parameters on the simulation results was discussed respectively.The W-Cu20 plate preparation by powder rolling was sintered,and the relative density,microstructure and mechanical properties of the sintered plate were investigated.The Drucker-Prager/Cap model of W-Cu20 powders was constructed on the basis theory of this model.Firstly,the morphology,particle size and phase of tungsten powders and copper powders were characterized,and then W-Cu20 powders was prepared by mixing(mass ratio 4:1)tungsten powders and copper powders.By the Brazil disc test and uniaxial compression test,the relationship between the parameters d and ? with relative density was obtained.The compression mould was also designed to measure the relationship between axial force as well as radial force and compressive strain in the process of powders compression in the mould.According to the formula,the relation of the model parameters R,pa and pb with the relative density was received.Finally,the spatial structure of Drucker-Prager/Cap with respect to relative density was given.In this paper,a numerical simulation model of W-Cu20 powder rolling was founded by finite element software Abaqus.First of all,the geometry modeling function of Abaqus was used to sculpt geometry and partitioned the geometry with resonable mesh.A temperature-displacement coupling analysis job was built.Then deformable geometry was endowed with Drucker-Prager/Cap model parameters.Subroutine VUSDFLD,written by FORTRAN,constantly updated W-Cu20 powders material properties during rolling process due to the change of relative density of W-Cu20 powders caused by powders deformation.According to the finite element simulation results,the law of W-Cu20 powder rolling was revealed.The influence proportion of process parameters on the simulation results were as follows: roll gap,rolling speed and rolling temperature.In the powder rolling process,the larger the roll gap,the greater the relative density of sheet,and the smaller the transverse displacement of the powders.With the increasing of rolling speed,the relative density of the sheets would decrease,the transverse displacement of powders would reduce,and the temperature field distribution would be more uniform.In the case of higher rolling temperature,the relative density of the plate would increase,and the flowability of the powders would raise.In this paper,W-Cu20 green strips was sintered at 1250?,1350? and 1450? for 2 hours respectively.The relative density of green sheet prepared under same rolling temperature rised from 4.63% to 11.87% when they was sintered under 1250? to 1450?.The relative density of W-Cu20 green sheet prepared under rolling temperature from 80?to 150?reduced from 11.87% to 5.3% under sintering temparature 1450?.The fracture strength of the sheet sintered at 1350 ? was 324 MPa,and the hardness was 224 HV.The microstructure demonstrated that tungsten was matrix in W-Cu20 alloy filled with copper powders in the pores.