Powder Metallurgy Fabrication Of SiC/CNTs Reinforced High-silicon Aluminum Alloy Composite

Al-Si alloy is a great development potential of the alloy, which has theadvantage of high specific strength, high wear resistance, low thermal expansioncoefficient, it has been widely used in automotive engine pistons, cylinder heads,connecting rods, compressor rotorthick silicon in Al-Si alloy seriously weaken themechanical properties of materials. The use of rapid solidification technology toprepare Al-Si alloy can refine the matrix grain and silicon size, thus improving themechanical properties of the alloy. Followed by thermal extrusion method of theabove three kinds of powder were made of the matrix alloy and composites, anddiscusses the influence of CNTs and SiCp on the microstructure of the three alloysat room temperature, high temperature conditions, microstructure, tensile properties,tribological properties and thermal expansion coefficient. In this paper, the Al-Sialloy and SiCp/Al-Si alloy heat treatment process is investigated.By optimizing the content of Al-Si alloy elements, the fine powder particlesand homogeneous alloy powder are obtained, and analyzed the powder phasecomposition and particle nucleation mechanism of the large size of the atomizationprocess. Through the adjustment of milling speed, ball to powder ratio and time toexplore the best milling parameters of the CNTs and the Al-Si alloy powder of CNTs2%(wt.%), ball to powder ratio of15:1, the process control agent (stearic acid)1%(wt.%), ball milling for2h; the best milling parameters of the SiC and Al-Si alloypowder of SiC2.5%(wt.%), ball to powder ratio10:1,100rpm for mixing powderfor15min,200rpm ball milling for3h, stopped for10min for1h by ball millingto obtain fine particles evenly reinforcements dispersed alloy powder, matrixpowder unoxidized.Ball milling of Al-Si alloy and its composite by450℃, upsetting, hot extrusiondeformation to complete the consolidation and the basic elimination of the gapbetween the powder extrusion ratio of10:1, the alloy remains small, Si phaseslightlygrow up, the needle phase in the powder disappear into short rod-like or flake.Hot extruded state of Al-Si alloy and its composites as the solution time toextend the hardness gradually decreased Si phase obviously grew up, the shapebecomes the dissolution of the second phase of the round and with small size, whileextrudedin parallel to the alloy extrusion direction, a small amount of themicrostructure after the solution began to disappear.Alloy after aging, the size of thelarge particles no significant change, while there are a large number of smallprecipitates appeared. Solution1.5h in495℃water quenching, natural aging of two days, the artificial aging temperature of120℃, the axial plane hardness of20h,the normal plane hardness in26hours maximum. At room temperature with thehighest strength and wear resistance of SiCp/Al-Si alloy, temperature increases, theAl-Si alloy has the highest strength and wear resistance, to reach300℃, the Al-Sialloy and composite strength converge. Al-Si alloy and its composites have goodhigh-temperature dimensional stability of SiCp/Al-Si alloy is slightly better than theother two alloys.