The Research On Compaction Mechanism Of 6061 Aluminum Alloy Powder

In recent years,the automotive industry has developed rapidly.Modern automotive structure design has taken energy conservation and emission reduction as the mainstream trend,and lightweight materials have received more attention.As an important lightweight material for automotive parts,6 series of powder metallurgy aluminum alloy has attracted wide attention due to its advantages of high lightweight,corrosion resistance,strong impact absorption and easy recovery.Powder compaction is an important process in powder metallurgy,which determines the density and mechanical properties of powder metallurgy products directly.In the process of powder compacting,the constitutive equation of material characterizing the deformation mechanism of powder is the basis of the numerical simulation method to research and analysis of powder compacting process,so the established powder compaction constitutive equation is of great significance to the rules of aluminum alloy powder compaction,optimization of mold design and process parameters.In this paper,through uniaxial compression,radial compression(Brazilian disc experiment)and die compaction experiment,the change rules of relevant material parameters with relative density were obtained and the Drucker-prager cap constitutive model was successfully established.By adding 6061 aluminum alloy powder material parameters with different densities,the simulation analysis of 6061 aluminum alloy powder compaction was carried out by Abaqus simulation software and secondary development of user subroutine USDFLD,and the correctness of the 6061 aluminum alloy cold compaction constitutive model was verified by the suppression force,displacement curve and the relative density distribution.When density is in the range of D≥0.75,the simulation precision is high,that is,the modified DPC model can more accurately describe the late suppression behavior of 6061 aluminum alloy powder.Then the experimental and simulation’s data of 6061 aluminum alloy powder cold compaction were fitted with Balshin’s,Kawakita’s,Gerongde’s,Hecker’s,Van Der Zwan’s,Shapiro’s,Huangpeiyun’s and Panelli’s compaction equation,and the results show that the Kawakita’s compaction equation is most suitable to describe the change of stress and density in 6061 aluminum alloy cold compaction.Considering that the compactness of the compacted billet obtained by 6061 aluminum alloy powder is about 0.96539 in theory,in order to further improve the densities of the compacted billet,the warm-compaction equation at 100 ℃ to 150 ℃ is derived by the concept of thermobarometric enhancement factor K.Friction also has a great effect on the stress during the actual compaction,so this paper further studies the pressure equation of μ(correlation of friction coefficient)based on ABAQUS numerical simulation.Combined with thermostatic enhancement factor K and friction coefficient μ,the equation of friction coefficient relative to the thermal pressure of 6061 aluminum alloy powder can be obtained.Finally,by changing the process parameters such as mould wall lubrication,compaction times and temperature,the paper explores the processing technology suitable for 6061 aluminum alloy powder compaction forming.It is concluded that the excellent compaction process of 6061 aluminum alloy powder is bidirectional single warm-compaction with zinc stearate alcohol lubricant at 100℃~150℃.The density induced by compaction can be effectively increased,the density distribution is uniform,and the phenomenon of adhesion to molds can be improved.