SHS Prepared Aluminum

Aluminum foam is a new kind of functional material with plenty of poresuniformly distributed in the aluminum matrix, due to its unique internalstructure,it has broad excellent performance, low density, high specificstrength,noise reduction by absorption and so on,showing profound potentialapplications in modern industry. Self-propagating high temperature synthesis(SHS),is a highly efficient new materials preparation technology,which ismainly used in the entity intermetallic compounds and the preparation ofceramic materials, however, there are far too few studies of the aluminum foamprepared by SHS.This paper is based on SHS technology to study the foaming process ofaluminum alloys under exothermic chemical reaction induced by precursormelting; To determine the highest proportion of aluminum powder in thecombustion system, experimental data analysis and calculation of the criticalcondition are investigated. To find the optimal combination of preparation,regulating the process parameters is investigated. The findings are as following:(1)In the preparation of aluminum foam by SHS,combustion temperatureand the amount of aluminum in the compact are the decisive factors forcontinuous reactions. The foam process is better with higher combustiontemperature and the larger aluminum with the lower combustion temperature.Successful foam process depends on the balancing of these two quantities.Experimental measurements indicate that the xAl+4Ti+B4C series will foamsuccessfully when the molar quantity of aluminum ranges from15to22in thesystem.(2)There are two roles of aluminum in the combustion system:firstly storingup to activate reactions between Ti and B4C.The second is to absorb heat andreduce the combustion temperature of the system. Much more liquid phase isproduced when there is too much aluminum in the process of combustion due tothe heat sink effect,leading to the reduction of temperature. In the front ofcombustion wave, the diffusion rate of reaction is slowed down because of theaccumulation phase. (3)On the basis of successful foaming, the control of compact density is animportant way to adjust pore morphology.The impact of compact density ismainly manifested in two aspects: the effective contact area belonging to thepowder particles will be changed, meamwhile heat and mass transfer behavior isaffected: the compact density also affects the microscopic characteristics ofpowder particles, such as the atom cluster size, particle size distribution andparticle shape etc. Experimental measurements indicate that precursor of66.5wt%Al is successfully foamed at2.0g/cm3~2.2g/cm3, pore roundnessuniform.(4)Based on the aluminum foam porosity as the research object, orthogonalexperiment is established to study the influence of the inner link of Ti content,compact density and Al content on the foaming process and deduce the optimalcombination of preparation process through theis analysis.The experimentalresults show that: the descending order of affecting factors is Al content,compact density and Ti content. The optimal parameters for preparation processof aluminum foam are the content of Ti and Al is7and21respectively withcompact density of2.2g/cm3.