Multi-particle Finite Element Modelling On The High Velocity Compaction Of Al/SiC Composite Powders With Core-shell Structure

In this paper,based on the plastic theory of metal powder materials and Johnson-Cook constitutive equation,the high velocity compaction(HVC)process of Al/SiC composite powders with core-shell structure was numerically reproduced using coupled DEM(discrete element method)and MPFEM(multi-particle finite element method)modelling from particulate scale.The variation of various macroscopic and microscopic properties of composite powder mass with different ordered and disordered initial packing structures was systematically studied.Initial packing structures of Al/SiC particles were firstly generated in DEM simulation,and then they were imported into the commercial FEM software MSC.Marc for configuration,including mesh division of individual particles,material property setting,contact definition between particles,loading process,and mesh re-division.The emphasis of current research lies in the characterization on the macroscopic and microscopic properties of the Al/SiC composite compacts during HVC from particulate scale,and the densification mechanism and temperature rising mechanism of the compacts were also comprehensively discussed and analyzed.The effects of initial packing structures,impact velocity,compaction pressure,and shell thickness(Al content)on the compact densification and temperature rise were systematically investigated.Meanwhile,the densification dynamics of the compacts,evolution and distribution of temperature with the impact velocity,rearrangement and deformation of the composite particles,pore filling behavior etc.were analyzed.Following results have been obtained.a)Compared with the HVC on Al and SiC composite powders obtained from normal mixing method,the HVC on Al/SiC composite powders with core/shell structures can realize the compacts with different properties,which including higher relative density,no agglomeration of SiC particles,and more uniform concentration distribution.b)During HVC on Al/SiC composite powders,the pores in the compacts are mainly filled by the plastic deformation of Al.While for different initial packing structures,their densification processes are different.For ordered initial packing,the arrangement of particles are ordered and dense,no obvious sliding phenomenon is observed during HVC;therefore.its densification process only includes two stages:particle deformation and hardening.And for the HVC on disordered initial packing,three stages in the densification process can be identified:i.e.particle rearrangement,deformation,and hardening.c)Even the effects of initial packing structures on the final relative densities of the compacts are not significant,they can create important influences on the early stage and middle stage of HVC.And the denser the initial packing structure is,the shorter is the time for particle rearrangement during HVC;otherwise,longer rearrangement time will be taken.In the final stage of HVC,the compaction curves tend to be coincidence,and the compaction pressure required for the final dense compacts is nearly the same.d)During the HVC process of Al/SiC composite powders,much higher temperature in the compact from dense initial packing structure can be obtained,and the temperature distribution is more uniform.In this case,the temperature rising rate is faster.This is mainly because with the increase of plastic strain rate,the heat is generated due to the increase of the resultant plastic strain work.The temperature rise during HVC is mainly caused by the plastic deformation of Al component and the friction between particles.And the faster the deformation of Al is,the larger is the temperature rise.Through computation one can find that when the compaction velocity is 10m/s,84.16%temperature is generated by plastic deformation.