Research On Structure Control And Sound Absorption Properties Of Novel Aluminum Foam

Aluminum foam material is a new type of metal material obtained by pure aluminum or aluminum alloy through a special process.Its excellent performance characteristics make it have broad application prospects in the field of materials.The object of this study is a new type of aluminum foam material.Through experimental optimization and verification,the optimal structural parameters are obtained.The sound absorption coefficient is tested to summarize the influence of the structural parameters on the sound absorption performance of aluminum foam.In this paper,a new type of foamed aluminum material was prepared by the "low-pressure infiltration method using calcium oxide as infiltration particles".Calcium oxide particles of three different sizes(large particles 2.00 to 2.50 m,medium particles 1.43 to 2.00 m,and small particles 0.90 to 1.43 m)were used as infiltration particles to prepare three pore sizes of aluminum foam test samples;as required the percolation equipment was improved,and the optimal process parameters were determined.The preheating temperature of infiltration particles was 720?and the temperature was maintained for 4 hours.The melting temperature of aluminum liquid was in the range of 680 ? 700? according to the difference of environment temperature.The appropriate infiltration pressure holding time,which is between60 s and 90 s,depends on the room temperature.The higher the room temperature,the longer the pressure holding time.The saturated aqueous solution of ammonium chloride was used to remove calcium oxide particles,and a calcium oxide removal device was designed and manufactured.The problems in the removal process were discussed.On the premise of ensuring the quality of aluminum foam,the process parameters were optimized.The removal efficiency was highest when the temperature of the removal solution was 80 to 90?and the average speed of the motor was 70 r/min.In this paper,two different testing methods are utilized to test the structural parameters of aluminum foam.The first is to adopt three-dimensional X-ray tomography technology to perform tomographic to obtain accurate porosity ratio,pore connectivity,and contact tightness between pores of the aluminum foam by tomographic reconstruction.The results verify that the structure of aluminum foam can be adjusted by mixing the slurry.Secondly,the self-designed air permeability coefficient test device was used to measure the air permeability coefficient of foamed aluminum material.The pore size,sample thickness showed a positive correlation with air permeability coefficient,and the porosity ratio showed a negative correlation with air permeability coefficient.The transfer function method was used to test the sound absorption coefficient of the new foamed aluminum material.The results showed that the relationship between the soundabsorption coefficient and the structural parameters complies with the following four rules:1.The new aluminum foam material has excellent sound absorption performance at high frequency.When the frequency is around 5000 Hz,the sound absorption coefficient reaches its peak,and when the frequency range is 5000 ? 6300 Hz,the sound absorption coefficient reaches more than 0.8.2.The thickness of the sample affects the sound absorption performance of the new aluminum foam material,and the sound absorption performance can be improved by increasing the thickness of the sample.3.Porosity affects the sound absorption performance of aluminum foam material to a certain extent.In the high frequency range,the sound absorption performance is less affected by the porosity;in the low frequency range,the larger the porosity,the larger the sound absorption coefficient,and the better the sound absorption performance.4.The pore size has different effects on the new aluminum foam materials in high and low frequency bands.In the high frequency band,the better the sound absorption performance with the increase of the aperture size,the peak value of the sound absorption can reach 0.98;in the low frequency band,with the increase of the aperture size,the sound absorption coefficient first decreases slightly and then increases rapidly.At 1600 Hz,the sound absorption coefficient is 0.5,and the sound absorption performance is well.