Study On Preparation And Impact Property Of High Volume Fraction SiC_p/Al Composites

Usually, the mechanical characteristics of material under dynamic loading are quite different from that under the static loading. Therefore, studying on the dynamic responses of composites is important including the deformation, high-speed machining, high-speed impacts, explode shaped and some high-speed manufacturing processes. A number of theoretical and numerical investigations have also been shown that composites reinforced by particles have high flow stress, while the flow stress values increased as the volume fraction of reinforcement increased. The high volume fraction particle reinforced composites have attracted attention because of their excellent dynamic impact property.In this paper, the infiltration process, interface reaction mechanism and microstructures of the SiCp/Al composites by pressureless infiltration technique were systematically investigated. The dynamic responses of 65vol.% SiCp/Al composites were studied with a split Hopkinson pressure bar in compression. The deformation microstructures of tested specimens were analyzed by using optical microscope. Deformation and damage mechanisms of the high volume fraction SiCp/Al composite were researched under different strain compressive loading. The main results and contributions of the paper are as follows:1. 60-70vol.% SiCp/Al composites were prepared by Al-Alloys melt infiltration into SiC particles porous preforms without external pressure. Experiments show that the detrimental interface reactions which result in the formation of the unwanted intermetallics Al4C3 can be retarded by the adopting of Al-Si5-Mg6 matrix and the surface treatment of SiC particles.2. At high strain rate of loading, the flow stress values of the SiCp/Al composites prepared by pressureless infiltration increased as the strain rate increased. The resultsshow that the composite material has strain rate sensitive flow stress behavior in the high strain rate regime when compared with quasi-static strain rates.3. The results have demonstrated that the flow stress and the yield stress of the composites strongly depend on the particles size and the composites reinforced by smaller particles (100μm) have high flow stress values.4. The optical microscope observations on the deformed samples shown that shear bands were formed in the composites reinforced with small particles (100μm) at 15% strain. The results show that the onset of deformation localization in SiCp/Al composites strongly depends on the particles size.5. At high strain rate of loading, the damage mechanism of the high volume fraction particle reinforced SiCp/Al composite associated with the fracture of the particles and the deformation localization of the matrix. The result indicated that the damage mechanism of SiCp/Al composite is considerably sensitive to particles size.