The Research Of Formation And Structure And Properties Of Aluminum Matrix Composite Pistons Reinforced With SiC Particles Fabricated By Centrifugal Casting

Piston is a key component in an engine, working conditions is very poor, ring groove and head section are prone to appear abrasion wear and fracture failure due to sever impact and friction. Aluminum matrix composite reinforced with SiC particles possesses a lot of excellent mechanical and physical properties such as high specific strength and specific stiffness, high wear and fatigue resistance performance, low thermal expansion coefficient, low density and high yield strength and good thermal stability and thermal conductivity. This issue hopes to improve the properties of piston by applying the advantages of SiC particles reinforced matrix composite to the piston. In this study, SiC particles reinforced hypereutectic and eutectic aluminum matrix composite slurry were prepared by stir casting method respectively, and then the centrifugal casting forming situation of piston at different casting process conditions for two kind of composite slurry were investigated. The pistons were solution treated and age treated. The macrostructure and microstructure of the pistons were analysised, hardness and wear resistance properties were measured. The effect of heat treatment on the properties of pistons was analysised. The thermal expansion coefficient of SiC particles segregation zone were measured. The results showed that:①Under four different casting conditions, the hypereutectic aluminum matrix composite formed well, while the eutectic aluminum matrix composite appeared sever defect. Compared to hypereutectic aluminum matrix composite, he eutectic aluminum matrix composite could achieve forming under lower temperature.②The hypereutectic aluminum matrix composite piston appeared significant sinter gathering zone, matrix alloy zone and SiC particles segregation zone only under the first three forming conditions, while the eutectic aluminum matrix composite piston appeared significant three zones under all of four casting conditions. The skirt section of he eutectic aluminum matrix composite piston existed large gas cavities while the hypereutectic aluminum matrix composite piston almost without gas cavities.③The microstructure of two composite piston were quite different from each other, for hypereutectic aluminum matrix composite piston, SiC particles appeared segregated phenomenon due to the presence of primary silicon and a large number of primary silicon assembled at the junction region, while this phenomenon didn't existed in eutectic aluminum matrix composite piston. ④The microstructure morphology were affected greatly by heat treatment while the morphology and distribution of SiC particles did not affected. After heat treatment, the microstructure of matrix alloy zone changed a lot, while the SiC particles segregation zone did not changed significantly.⑤The hardness of pistons were improved a lot after heat treatment, the increased extent of matrix alloy zone was larger than that of SiC particles segregation zone. The increased extent of hypereutectic aluminum matrix composite piston was larger than that of eutectic aluminum matrix composite piston.⑥The wear extent of the SiC particles segregation zone reduced while the matrix alloy zone increased after heattreatment.⑦The linear expansion coefficient of SiC particles segregation zone is much lower than that of matrix alloy.