Study On Properties Of Aluminum-graphite Self-lubricating Composite Prepared By Die-casting Infiltration Process

Aluminum alloy has been widely used in many fields due to its high specific strength,low density and good ductility.However,the low wear resistance of aluminum alloys limits its application in many environments such as high temperature,heavy load,high speed,or insufficient lubrication conditions.But the aluminum-graphite self-lubricating composite material can effectively break through the original shackles,so that the material has a lower friction factor and excellent wear resistance.By using the die-casting impregnation process,the molten aluminum is hydraulically inserted into the horizontal die-casting machine mold with solid lubricating components with an injection force of 65 MPa,and the pressure is maintained for 15 s.Finally,two aluminumgraphite self-lubricating composite materials with a size of ?30 × 40 mm were prepared.The hardness and density of the two aluminum-graphite self-lubricating composite materials are not much different from those of the matrix alloy,however,due to the addition of graphite with high thermal conductivity,the thermal conductivity of the self-lubricating composite material has increased significantly,with a maximum increase about 27 %.The study found that the form of graphite is vary in the two self-lubricating composite materials.In the aluminum-carbon felt self-lubricating composite material,graphite is mostly short rod-shaped or elliptical,while in the aluminum-porous carbon self-lubricating composite material,most of it exists in a sheet structure,and it is found that the tail of the scaly graphite structure has a bad combination with the basic aluminum alloy.In addition,the grain size of aluminum-porous carbon is too large,so that the crushing strength of material is only 169.02 MPa,and the ultimate strain is about 8 %,which is much inferior to aluminum-carbon felt self-lubricating which has a crushing strength of 285.23 MPa and an ultimate strain of 17 %.From the perspective of the macroscopic fracture morphology,the aluminum-carbon felt self-lubricating composite material and the matrix alloy is a significant feature of plastic fracture,while the fracture of aluminum-porous carbon is a typical brittle fracture failure.The friction test results of the materials show that the friction factor and wear rate of the two self-lubricating composite materials are lower than the aluminum alloy matrix.Among them,the friction factor and wear aluminum of the aluminum-carbon felt self-lubricating composite material are lowest.It's lowest friction factor and wear rate are respectively 43%and 5% of the aluminum alloy matrix.At room temperature,the wear mechanism of the aluminum alloy matrix is adhesive wear.At 200 ?,the wear mechanism changes to furrow wear.The wear mechanism of the two self-lubricating composite materials belonged to abrasive wear during the whole experiment.The pressure and high temperature coexisting die-casting infiltration process used in the preparation process can greatly improve the bonding stability of aluminum and graphite,and the production cycle of less than one minute can effectively control the production of additional products.The research results of this paper and the systematic analysis and comprehensive exploration of the tribological characteristics and mechanism of aluminum-graphite self-lubricating materials will have important research significance for the development of new aluminum-based graphite self-lubricating composite materials.