Research On Regulation Mechanism Of Compression And Sound Absorption/insulation Properties Of Closed-cell Aluminum Foam

Closed-cell aluminum foams as a kind of structure-function integrated new material possess light weight,high specific strength,energy absorption and vibration damping,excellent flame resistant properties.The combination of these properties makes closed-cell aluminum foams attractive in the fields of transportation,aerospace and construction.In recent years,with the development of high-speed railway,security and comfort of passengers gradually cause extensive concern of researchers.Closed-cell aluminum foams possess excellent combination properties and are considered to be an ideal structure material for application to high-speed railway.Nevertheless,the distributions of pore structure,mechanics and sound absorption properties of closed-cell aluminum foams have not achieved the desired results and further research is needed.Scanning electron microscope with energy disperse spectroscopy and other analysis methods were used in this present study.First,from the view of pore structure control,titanium hydride(TiH2,foaming agent)was pretreated in different temperature(673-833 K).The decomposition behavior and phase composition of original and pretreated TiH2 were analyzed.The effects of pretreatment temperature of TiH2 on pore size distribution of closed-cell aluminum foam were discussed.The relationship between decomposition behavior of TiH2 and pore size distribution of closed-cell aluminum foam was revealed.The effects of pretreatment temperature of TiH2 on quasi-static compressive properties of closed-cell aluminum foam were discussed and the optimal pretreatment temperature of TiH2 was 753 K.On this basis,in order to improve mechanical properties of closed-cell aluminum foam,closed-cell aluminum foams with different percentages(0.00-0.90 wt.%)of erbium(Er)element are successfully prepared.The distribution and existence form of Er element in aluminum foams were revealed.The mechanical properties of closed-cell aluminum foams were obtained with different contents of Er element and the strengthening mechanisms were found.The optimal range of Er element in aluminum foam is 0.10-0.50 wt.%.On the other hand,closed-cell aluminum foams with different contents(0.0-1.0 wt.%)of multi-walled carbon nanotubes(MWCNTs)were fabricated by using modified melt foaming method.The optimal ball-milling parameters of mixture with MWCNTs and aluminum powders were confirmed by orthogonal test.Furthermore,the existence forms of MWCNTs in closed-cell aluminum foam were observed and summarized,which was beneficial to characterize the wettability between MWCNTs and aluminum matrix.Moreover,mechanical properties of closed-cell aluminum foam with different contents of MWCNTs were contrasted and the optimal content was obtained.Besides,the functional application of closed-cell aluminum foams was considered in this work.Different perforation and air gap types were used for changing the macrostructures of the foams,and their effect on the sound absorption coefficient and sound reduction index were investigated.The sound absorption and sound insulation properties of closed-cell aluminum foams with different macrostructures were analyzed simultaneously and the relationship between acoustic properties and macrostructure of closed-cell aluminum foam were established.Meanwhile,according to the experiment result,the propagation structural models of sound waves in closed-cell aluminum foams with different macrostructures were built and the influence of macrostructures on acoustic properties was discussed.This study is contributed to provide theoretical and technical support for application of closed-cell aluminum foam.