Preparation And Properties Of Porous Foamed Aluminum With Controllable Pore Structure

As an important method for preparing foamed aluminum,the invention has the advantages of simple preparation process,controllable porosity,high operation safety,wide material applicability and easy realization of large-scale production.In this paper,sodium thiosulfate(Na₂S₂O₃)is used as raw material of pore-forminggent to replace the traditional pore-forming agent(such as urea,salt).Firstly,Na₂S₂O₃was melted and injected into the designed silica gel mold to obtain pore-forming agents of different shapes and sizes.Secondly,the pore-forming agent and aluminum powder are pressed according to a certain proportion to obtain a composite preform.Thirdly,the pore-forming agent was dissolved in the aqueous solution at a certain temperature,and the blank sample of aluminum foam was obtained.Finally,the blank sample was sintered according to a certain heating standard to obtain aluminum foams with the same pore structure as the pore-forming agent.The pore structure,metallographic analysis and quasi-static compression tests were conducted.The preparation of aluminum foam with Na₂S₂O₃as poreforming agent and urea as poreforming agent was compared.The research results showed that:(1)Sodium thiosulfate can be used as a good pore-forming agent for preparing foamed aluminum.Sodium thiosulfate has a low melting point,is easily soluble in water and is non-toxic.Using 3D printing and turning silica gel mold technology,a pore-forming agent with arbitrary shape and size can be prepared,so as to control the pore structure of foamed aluminum.Foams with three porosity(65%,70%and 75%)and three pore sizes((?)2mm,(?)3mm and(?)4mm)were prepared.(2)Under the experimental conditions,the best water bath temperature for removing pore-forming agent is 60?.The time of dissolving and removing the pore-forming agent for aluminum foam blank with porosity greater than 70%is2 h,and that for the aluminum foam blank with porosity greater than 70%is 6h.With the decrease of porosity,the number of through-holes in aluminum foam will also decrease.The sintering temperature of foamed aluminum blank is600?-620?,and the sintering time is 2.4 hours.(3)The aluminum foam prepared by Na₂S₂O₃has a good pore structure and the compressive stress-strain curve is stable.The deformation of cellular pores of aluminum foam prepared by using urea as a poreforming agent is serious,and the surface of the sample is prone to crack,fracture or bending,and the fluctuation of compression stress-strain curve is obvious.The platform pressures are close to each other.(4)The influence of porosity on the mechanical properties of foamed aluminum is greater than that of pore size.With the increase of porosity,the mechanical properties of foamed aluminum decrease.The influence of pore size on the mechanical properties of aluminum foams is affected by porosity,and there is an interaction between porosity and pore size.