Study On Pore Structure Control Technology And Mechanism Of APM Foam Aluminum Pellets

Aluminum foam with closed pore and high porosity can be prepared by Powder Compact Melting(PCM)method.It has the advantages of stable preparation process,easy to make near-final parts and easy to form composite structure.The obtained aluminum foam has excellent energy absorption performance,sound insulation performance and electromagnetic shielding performance,etc.The porosity,pore size and uniformity of pore structure of foamed aluminum alloy have great influence on these properties.The results show that the liquid drain phenomenon exists in the process of PCM method,which affects the uniformity of the pore structure of the product.The larger the size of aluminum foam,the more serious the drainage phenomenon.In this paper,aluminum foam balls with different silicon composition and different sizes were prepared by PCM method,and the factors affecting the pore structure of aluminum foam were analyzed in order to solve the drainage phenomenon in the foaming process and obtain Advanced Pore Morphology(APM)of aluminum foam balls.The control technology and mechanism were studied.The results show that:1)The discharge phenomenon in the process of PCM method foam aluminum foaming process was well solved by preparing foam microcaphers,and APM foam is available.The test can obtain a more uniform size range of 5mm to 15 mm,and it is found that when the temperature of the predetermined furnace is 700 ° C,the size of 10 mm is 12 mm,the mass fraction of Si is 12%,the prepared APM foam is small.The ball is in the best,and the hole structure is most uniform.2)The expansion process of APM foam aluminum pore structure can be divided into four stages: inoculation zone,foaming zone,spherical retention period and deformation zone.The control mechanism includes: sintering crack fusion theory and pore formation and pore merging theory in the foaming stage,liquid film theory for bubble pore pattern control,and timely solidification theory for bubble stability.The selected size,the foaming temperature and time controlled by the preset furnace temperature,and the base material of the alloy all contribute to these mechanisms in different foaming stages3)The forming mode of the preform affects the pore structure of the aluminum foam.It is found that the density of the preform obtained by rolling method is higher than that obtained by hot extrusion method,and the distribution of foaming agent is more uniform,which makes the pore structure of the aluminum foam more rounded and uniform.4)The addition of 0.1wt % graphene in the preform can effectively refine the pore size of the aluminum foam pellets,increase the nucleation rate of the pores,and improve the uniformity of the pore structure.5)The hole structure uniformity of the APM foamed aluminum ball affects the compression performance of the ball,which specifically manifests the fluctuation stability of the platform region load,and the load fluctuations have a more uniform aperture structure.The load-strain curves of spheres of different sizes are different,and the load-strain curves of different sizes have laws: the larger size,the larger platform area is higher.