Study On Preparation And Properties Of Aluminum Matrix Composites Reinforced By Multiphase Intermetallic Compounds

Due to its high strength,high wear resistance and other properties,the application proportion of aluminum matrix composites(AMC s)in aerospace,transportation and other fields has increased significantly.Most of the AMCs were prepared by powder metallurgy at present,but there are very few reports on traditional casting technology.Therefore,this article is mainly devoted to the preparation of multi-phase intermetallic compound reinforced aluminum matrix composites by adding high-entropy alloys into the aluminum alloy using traditional casting technology.In this paper,the AlCoCrFeNiTi HEA and AlSiTiCrNiCu HEA were respectively added into pure aluminum and AlCoCrFeNi HEA was added into 6061 Al alloy to prepare AMCs.With the help of testing apparatus such as optical microscope,scanning electron microscope(SEM),electron probe microanalysis(EPMA),transmission electron microscope(TEM),tensile testing machine and friction testing machine to analyze the microstructure,mechanical properties and tribological behavior of AMCs.the conclusions obtained are as follows:When AlCoCrFeNiTi HEA was introduced into pure aluminum,flake-like and blocky intermetallic compounds precipitated distributing on ?-Al matrix during solidification,and the amounts of intermetallic compounds increases with the increase of the AlCoCrFeNiTi HEA addition.In addition,the rod-like phase with diameter of less than 200 nm distributed inter-dendrite of ?-Al.The grain size of ?-Al also decreases with the increase of the HEA addition.The mechanical properties of AMCs will also change with the addition of HEA.The tensile strength first increased and then decreased.After adding 5.0wt.%HEA,the tensile strength increased by 193.1%from 58MPa of pure aluminum to 170 MPa.While the elongation decreased with increased HEA addition.when 6.0wt.%HEA was added into pure aluminum,the elongation decreased from 40.6%to 22.7%.In addition,the tribological behavior of AMCs under seawater conditions was studied.The coefficient of friction(COF)and wear rate decrease with the increase of the HEA addition.When the addition reached 6.0wt.%,the COF of AMCs decreased by 71.1%from 0.83 to 0.24,and the wear rate decreased by 90.8%from 2.48×10-9m³N^-1m^-1 to 2.27 × 10-10 m³N^-1m^-1.After adding AlSiTiCrNiCu HEA into pure aluminum,multi-phase intermetallic compounds(Al₃Ti,Al70Cr20Ni10,AlTiCrSi,Al2Cu and Al7Cu4Ni)were precipitated,of which Al₃Ti,Al70Cr20Ni10 and AlTiCrSi were distributed on the matrix,while Al2Cu and Al7Cu4Ni distributed inter-dendrite of ?-Al,the grain size of ?-Al is also significantly reduced.As the amounts of HEA increased,the volume fraction of intermetallic compounds increased,and the grain size of ?-Al gradually decreased.The compressive strength of AMCs is positively correlated with the addition of HEA,while the compressibility is negatively correlated.When the addition reached 20.0wt.%,the compressive strength is up to 530MPa while maintaining good compressibility(greater than 25%).Dry sliding friction experiments illustrated that the COF and wear rate of AMCs decreased with the increase of the HEA addition.When the addition of AlSiTiCrNiCu HEA is 20.0wt.%,the COF reduced from 2.51 of pure aluminum to 0.66,which is reduced by 73.7%,and the wear rate reduced by 90.5%from 4.86×10-13m³N^-1m^-1 to 0.4 6 ×10-13mW3N-1m-1.After the AlCoCrF eNi HEA was added into 6061 Al,the flocculent five-element intermetallic compounds AlCoCrFeNi and the strip and blocky intermetallic compounds AlCoNiFe precipitated on the matrix.With the increased of the HEA addition,the number of intermetallic compounds also increased.In addition,the compressive properties of AMCs significantly improved with the addition of HEA,and the compressive strength continues to increase while maintaining good compressibility.The dry sliding COF and wear rate of AMCs also decrease with the increase of HEA addition.When the addition was 15.0wt.%,the COF decreases from 1.78 to 0.62,and the wear rate decreases 2.56×10^-13m³N^-1m^-1 to 6.4×10^-14m³N^-1m^-1.