Three-dimensional Numerical Simulation Of Densification Process Of Cu-Cr Powder

Densification of Cu-Cr powder during the test,the change in particle morphology of the internal extrusion was not recognised.Through the characterization of three-dimensional particles and finite element analysis,it is possible to effectively solve the visualization process of the change process inside the test material in the three-dimensional macroscopic simulation.In this paper,nonlinear finite element Marc software is used to analyze the complex densification process of Cu and Cr particles from a microscopic point of view.Firstly,the finite element model of Cu and Cr particles was constructed,and the Cu and Cr finite elementary particles were assembled into a staggered and aligned Cu-Cr powder particle model.The effects of single-two-way densification process on the density of(compressive force,friction coefficient),the equivalent plastic strain of the particles in the densification process and the flow law of the nodes were studied.The correctness of the model is verified by experiments.The densification of the misalignment and aligned Cu-Cr powders under different environments(compression force,friction coefficient,temperature)was studied,and the misalignment and aligned Cu-Cr powder particle models were compared and analyzed.Squeeze flow deformation of particles and nodes during the process.The main results of the paper are as follows:(1)The Cu-Cr powder particles in the unidirectional pressing process make a larger amount of bidirectional compression and a higher density.When the pressing force is 40 MPa,the relative density of the unidirectional pressing process is 95.8298%,the relative density of the two-way by pressing is 89.0782%,and the unidirectional density is 6.7516% higher than the two-way.In the densification process ofmisalignment Cu-Cr powder particles,the initial pressing efficiency of the unidirectional identified Cu-Cr powder particles is high,and the two-stage densification Cu-Cr powder particles have high pressing efficiency in the middle and late stages.The simulation results are consistent with the experimental results,verifying the accuracy of the model.(2)The increase of friction coefficient is conducive to the close bonding between the particles of unidirectional compacted Cu-Cr powders and the increase of the density of the particles of Cu-Cr powders.In each incremental step,the difference of deformation of the two-way compacted Cu-Cr powder is 0.5761,which is much smaller than that of the one-way compacted Cu-Cr powder 1.7327.The strain at the initial stage of extrusion is mainly located at the X-end of the extrusion direction.With the densification proceeding,the particles rearranged in the preliminary extrusion stage to form dislocation extrusion,and the dislocation of the pressed Cu-Cr powder particles can fully fill the voids.The joint fluidity of densification of unidirectional compacted Cu-Cr powders is relatively high.However,while identified joints of two-way compacted Cu-Cr powders flow symmetrically and extrudedly with respect to the intermediate particles,and the fluidity of the joints is low.The fluidity of identified Cu-Cr powders,especially the flow of nodal particles(the uniformity of particle deformation),plays a key role in the densification of powder.(3)It is necessary to rule the overall flow of the nodes of the Cu-Cr particle model.In the initial stage of the displacement of Cu-Cr particles,lateral particle slip and particle rearrangement mainly occurred,and the rotational flow of the particles was more obvious than that of the Cu-Cr powder particles and the fluidity was larger.After the rearrangement,the particles mainly undergo plastic deformation.which are forced to extend the gap during the extrusion deformation process,and the particles are squeezed to each other to undergo a slight reciprocating motion,and gradually become steady state.The flow of the particle nodes decreases as the density increases.The identified Cu-Cr particle model after densification has better particle uniformity than the Cu-Cr particle model.(4)Densification of staggered Cu-Cr powder particle model at ambient temperature and constant temperature.Under the condition of warm powder cold mold,the higher the temperature of the particle,the higher the density;under the fiery powder temperature mode,the temperature of the particle is higher.The higher the density,the lower the density.The density of the warm powder cold mold is generally higher than that of the warm powder warm mold(constant temperature environment),the density is0.3630% at 100 ?,and the density is 2.8700% at 800 ?.The coefficient of friction affects the misalignment and the densification of the Cu-Cr particles.When the friction coefficient is 0.1,the density of the staggered Cu-Cr particle model is up to 95.6859%.When the friction coefficient is 0.5,the density of the Cu-Cr particle model is up to97.5343%.