Fabrication And Mechanical Properties Of Aluminum Matrix Composite Foams

The pure Al foam reinforced by SiC particles was prepared by spark plasma sintering(SPS)and dissolution with NaCl as space holders.The effects of sintering process on the densification of mixed powder and the optimal sintering process parameters were analyzed by scanning electron microscopy(SEM)and X-ray diffraction analysis(XRD).By using the DNS-100 universal tensile testing machine and MS-2000 raoting friction instrument,the compressive and friction properties of the SiC/Al composite foams were respectively studied at room temperature.Moreover,the compression and friction properties of SiC/Al composite foam with different porosity,different SiC particle weight percentage and SiC particle size were investigated.Then the influence mechanism of SiC particles on its compression properties,deformation process and friction properties was discussed.The experimental results show that:By analyzing the sintering process and relative density of the SiC/Al composite foam,temperature is the main influencing factor in the early stage of sintering.The results showed that the SiC/Al composite foams with relative density of 97.6%and excellent performance can be prepared by SPS at 550℃ for a dwell time of 10 min at an external pressure of 30 MPa in vacuum.The compression tests show that the compressive yield strength of pure aluminum foam is 10 MPa.Under the same porosity,SiC/Al composite foam has higher compressive yield strength.Using SiC particles with the size of 20μm as the strengthening phase,when the addition amount is 10wt.%,the compressive yield strength of SiC/Al composite foam is up to 58MPa,and the yield strength is increased by 4.8 times.Using SiC particles with the size of 20μm as the strengthening phase,when the addition amount is 10wt.%,the compressive yield strength of SiC/Al composite foam is up to 120MPa,and the yield strength is increased by 11 times.The compression fracture morphology shows that the compression fracture of SiC/Al composite foams mainly emerge in two parts.One of them is the ductile fracture of the matrix metal,and the other is the debonding crack the interface between SiC particles and the matrix metal.In the compression process,the SiC particles hinder the elongation of the crack,so that the compressive yield strength of the aluminum foams are enhanced.However,as the addition of SiC particles increases,brittle fracture between the SiC particles and the base metal increases,resulting in a decrease of compressive yield strength.When SiC particles with the size of 20 μm are used as the strengthening phase,debonding cracking tends to occur between the reinforcement and the substrate interface.Compared to the reinforcing effect of SiC particles with the size of 0.5μm,the enhancement is poor.When 0.5 μm particle size SiC particles was used as the strengthening phase,the SiC particles easily agglomerates as the amount of addition increased,resulting in a decrease in yield strength.The friction tests indicated that the average friction coefficient of pure aluminum foam is 0.45 at a porosity of 40%.While,the average friction coefficient of SiC/Al composite foam is significantly reduced.Using SiC particles with the size of 20μm as the strengthening phase,when the addition amount is 10wt.%,the average friction coefficient of SiC/Al composite foam is about 0.34,and the wear resistance is increased by 31.9%.Using SiC particles with the size of 20μm as the strengthening phase,when the addition amount is 10wt.%,the average friction coefficient of SiC/Al composite foam is about 0.32,and the wear resistance is increased by 38.7%.The wear scar morphology shows that the SiC particles bear the role of the skeleton in the metal matrix.During the wearing process,The hardness of SiC and the softness of carbon are helpful to reduce the friction coefficient.During the wear process,small cracks are formed on the surface of the sample,and SiC of smaller particles is more easily detached from the surface of the substrate.Hence the improvement effect of the 20 μm particle size SiC particles is better.