The Influence Of Graphite On Dimensional Stability And Mechanical Property Of SiCp/Gr/2024Al Composites

As dimensionally stable materials, SiCp/Al matrix composites have been applied on precision instrument. SiCp/Al matrix composites have a worse machinability because of the addition of hard SiC particle. Based on this background, a novel sort of SiCp/Gr/2024Al composites was fabricated by squeeze casting method with flaky graphite particle of different size and volume. The influence of graphite on properties of the composites was discussed in this paper, such as microstructure,dimensional stability and mechanical property.The microstructure of SiCp/Gr/2024Al composites under different heat treatment process was studied by transmission electron microscope, compared with the microstructure of SiCp/Al matrix composites. The result of TEM observation indicated, precipitated phase of SiCp/Gr/2024Al composites treated aging for 10 hours was dispersed in the form of small size and high density and a low dislocation density appeared in the matrix. The composites treated aging for 24 hours has a microstructure feature of big size precipitated phase and less distributed, while it was not observed that precipitated phase was relatively small and dense in the microstructure of the composite treated by thermal-cold cycling.Compared with SiCp/2024Al composites, the dimensional stability of the SiCp/Gr/2024Al composites was investigated under the condition of alternative temperature and static load respectively. The research indicated that SiCp/Gr/2024Al composites by treated for 24 hours gained the best dimensional stability under alternative temperature condition, the micro-yield strength of the SiCp/Gr/2024Al composites treated by three different heat treatment processes except for annealing doesn't changes obviously.Mechanical property and fracture behaviors were investigated by tensile test and obversion of SEM fractography. The effect of volume fraction and size of graphite on tensile strength and elastic modulus were analyzed. With the increase of volume fraction, the tensile strength was decreasing as well as elastic modulus. The tensile strength of SiCp/Gr/2024Al composites by aged for 10 hours was the highest value during the different heat treatment processes. The size of graphite in 1μm, 6μm, 20μm and 70μm, the tensile strength of the composites with 6μm...