Microstructures And Mechanical Properties Of Powder Extruded SiC_p/2024Aluminium Matrix Composites

In order to meet the requirements of some structural products, plastic processing isnecessary for particle reinforced aluminium matrix composites prepared by techniques asstir casting. But powder extrusion process is a new technique to prepare materials, whichcombines powder metallurgy with hot working well in a step. The process is simple andshort with low energy consumption. And the materials prepared by this process have highrelative densities, uniform microstructures and little (or no) segregation. Up to now, therewere some applications of extrusion to prepare magnesium alloy, aluminium alloy, andcemented carbide and so on, but there is no report about the study of powder extrudedSiCp/2024aluminium matrix composites. In this work, SiCp/2024aluminium matrixcomposites were prepared by powder extrusion process, and the effects of processparameters on the microstructure and tensile properties were studied. The heat treatmentprocess of SiCp/2024aluminium matrix composites prepared by powder extrusion wasoptimized, and its wear behavior was analyzed as well.Firstly, SiCp/2024aluminium matrix composites were prepared by powder extrusionprocess at different extrusion temperatures or extrusion ratios. The effects of extrusiontemperature, extrusion ratio, and volume fraction of SiC particles on the microstructures andtensile properties were investigated. The results show that SiC particles are distributeduniformly in the matrix of composite. The relative density, hardness and tensile properties atroom temperature increase with increasing extrusion temperature. When the extrusion ratiois λ=17.36and the extrusion temperature is500℃, the tensile strength, yield strength andelongation after T6heat treatment reaches462MPa,425MPa and3.71%, respectively.Increasing extrusion ratio appropriately can improve the interface bonding state betweenSiC particles and matrix alloy. The relative density, hardness and tensile properties at roomtemperature increase with increasing extrusion ratio. When the extrusion temperature is480℃and the extrusion ratio is λ=40, the tensile strength, yield strength and elongationafter T6heat treatment reaches502MPa,441MPa and5.04%, respectively. The aggregationphenomenon becomes remarkable and the relative density decreases when the volume fraction of SiC particles increases. The hardness and strength increase with increasing SiCcontent in composite, but the elongation decreases at the same time.The heat treatment process of powder extruded SiCp/2024aluminium matrixcomposites was studied. The results show that the optimal heat treatment processingparameters for SiCp/2024aluminium matrix composites prepared by powder extrusion areas follows: solution at490℃for75min and aging at170for8h. After this heat treatment,the tensile strength, yield strength and elongation of the composite, which contains20vol%SiC particles and was prepared at extrusion temperature480℃and extrusion ratio λ=17.36,reaches457MPa,420MPa and3.55%, respectively.The wear behavior of SiCp/2024aluminium matrix composites was studied. Theeffects of the volume fraction and the average size of SiC particles on the wear properties ofSiCp/2024aluminium matrix composites, and the wear mechanism is investigated. Theresults show that under the dry sliding condition, the depth and width of the wear scar andthe wear volume of the composite decrease with increasing volume fraction of SiC particlesin the composites. But they decrease at first and then increase with increasing average sizeof SiC particles. When the average size of SiC particles is about10μm, the wear volumereaches the minimum, which indicates that the abrasion resistance improves as the volumefraction of SiC particles increases. The wear resistance is the best when the average size ofSiC particles is10μm. Under the dry sliding condition, abrasive wear is the mainmechanism of the composite prepared by powder extrusion. And there is adhesive wear aswell.