Title: Features of the process of compaction of powder aluminum alloys by cold pressing

Abstract

A schematic model of the compaction process of spherical particles of different sizes is proposed. In this regard, the process of compaction of granules was considered in the context of three stages. It has been found that in the first stage there is an active compaction, as a result of which the packing of the powder particles becomes tighter. At the second stage, as a result of an increase in the pressing pressure, the contact areas of the particles increase and juvenile friction surfaces are formed, which enhances their molecular interaction and friction resistance. At the transition of pressing from the 2nd stage to the 3rd, the generated pressure strengthens the mechanical contacts and causes the extrusion of particles into the micropores of the pressing. Large differences between pellet sizes improve the extrusion of fine particles. The analysis of changes in some mechanical parameters of a porous composite material based on aluminum, depending on the applied pressure during compaction, is carried out. With the help of special devices based on compression models proposed by different researchers, the change in the relative density of the porous material depending on the pressing pressure was studied. In conventional and semi-logarithmic coordinate systems, graphical descriptions of the dependences of the relative density of briquettes on the pressing pressure, as well as their initial microhardness on the particle size, are given. In addition, curves were presented that characterize the effect of pressing pressure on both the microhardness of briquettes with different fractions and their shear and compressive strength. Calculation formulas are given that make it possible to calculate the areas of initial and current pores, depending on the particle size of the constituent fractions, at any moment of load application until the powder is completely compacted.