Computer Simulation Of Powder Metallurgy Process Based On Comsol Multiphysics

Powder metallurgy is a green manufacturing technology.Powder compaction and sintering are two very important partion in the powder metallurgy process.since powder compacted compact is not the final process of powder metallurgy,its performance greatly affects the final product performance.Sintering is the subsequent treatment of the compact after powder compaction.The particles are bonded by heating and the powder are strengthened by the migration of the material,it result densification and recrystallization.In this paper,the numerical simulation and computer simulation of metal powder compaction process and spark plasma sintering process are mainly carried out.The development status and application of powder metallurgy technology,the current status of numerical simulation of powder forming process,the mechanism and research status of spark plasma sintering are systematically described.On this basis,the powder forming modeling,yield criterion,mechanical model and related theories are analyzed,and the mechanical model and related theories are summarized,and the modeling method based on the elastic-plastic finite element method is determined.The finite element?FEM?software COMSOL Mulitphysics is used to simulate the powder compaction process at the macro and micro scales respectively,and the problem of particle motion and deformation during powder compaction process is successfully solved.In this process,the influences of the pressing method?unidirectional pressing,bidirectional pressing?and the pressing force on the particle motion and volume plastic strain are discussed.Two finite element models are established based on different mechanical models.a continuum particle model using the FKM-GTN yield function to characterize the porosity of porous materials,and a mesoscale discrete particle model.Using COMSOL Multiphysics software to define the material properties of the powder compact under the two models,set the initial conditions and boundary conditions,and set the contact model and related parameters.By continuously optimizing the simulation process,it is difficult to converge in the calculation process,and the powder compaction is successfully simulated.The results as follow:?1?as the punch descends during the powder pressing process,the porosity decreases,the powder is gradually compacted,and the overall compaction is displaced and elastically deformed,and the individual particles are plastically deformed due to extrusion.?2?The interfacial friction force has a significant effect on the particle deformation in the contact area with the mold wall interface.?3?The compaction of compacted compacts is the result of the combined effect of multiple factors.Only increasing the compacting force cannot increase the density of compacted compact indefinitely.During the compacting process,an appropriate compacting force should be selected according to the characteristics of the powder.?4?There is a large difference between the volumetric strain of particles at different positions during the pressing process.The use of two-way pressing is more conducive to the uniformity of the compact density.Spark Plasma Sintering?SPS?,also known as field-assisted sintering or pulsed current sintering,is a consolidation process that uses both uniaxial pressure and pulsed current to generate Joule heating,and its sintering rate is much higher than traditional sintering technology.From a simulation perspective,SPS sintering is a multiphysics coupling model involving electric field,temperature field,and solid mechanical field.In this paper,the FEM model with electric field,temperature field and solid mechanics physical field is established by using COMSOL Multiphysics and combining the characteristics of SPS.By setting contact properties,initial conditions,boundary conditions and related parameters,the electric field and temperature field distributions of the Al₂O₃ sample and the core part of the sintering system were successfully simulated.The results show that:?1?The temperature distribution inside the powder compact is directly related to the electrical conductivity of the material,and the current distribution pattern hardly changes with time.The type of current distribution largely depends on the powder compact and the resistance of mold.Al₂O₃powder is a non-conductive material,which is directly heated by heat conduction instead of the Joule effect.?2?Joule heat is the main source of heat in spark plasma sintering.Temperature distribution is an important parameter affecting the microstructure and mechanical properties to the sintered materials.The maximum temperature is at the position where the cross section of the punch decreases,and the radial temperature gradient of the sample is relatively large.