Research Of Young's Modulus And Damping Mechanism Of SiC_p/Al Composites

The SiC_P/6066Al composites reinforced by different surface-treated SiC particles were fabricated by a powder metallurgy route.The microstructures and mechanical properties of the composites were studied by optical microscopy(OM),scanning electron microscopy(SEM),transaction electron microscopy(TEM),X-ray and tensile test,respectively.Dynamic modulus and damping mechanism of 12%SiC_P/6066Al composites were analyzed by multifunctional internal friction measurement(DMA). The effects of interfacial features,namely,the interfacial thickness and bonding strength, on particle reinforced metal matrix composites were explored by theoretical model compared with experimental results.Some major conclusions can be drawn from the experimental studies and the theoretical analysis as follows:(1) The SiC particles with clean and coarsened surfaces and blunted angles were obtained by surface treatment techniques of oxidation,acid dipping and alkali washing. The SiC/Al interfaces formed by Al atoms diffusion into SiC particle surfaces during the hot-pressing and hot extrusion process were thin and clean.The bond strength of SiC/Al interfaces was strong.SiC particles were homogeneously distributed in Al matrix,and Al matrix was refined more during the hot extrusion process due to the presence of tough particles.(2) The activation energy and relaxation time of the internal friction peak in SiC_P/6066Al composites and 6066Al alloy were obtained,1.78eV and 9.95×10^-15s for the composites,and 1.68eV and 1.01×10^-14s for the unreinforced alloy,respectively.The internal friction peaks in the composites,compared with that of the alloy,shifts to low temperature about 50℃.The damping capacity of the composites is superior to alloy in low and medium temperature range due to the dislocation motion.The dynamic modulus of the composites softens more slowly than that of the alloy,which attributes to high temperature properties of SiC particles,and the corresponding softening ratios are -0.69℃^-1 and - 1.60℃^-1 at high temperature,respectively.(3) Whether including the volume of interface in the reinforcements or not, Young's modulus of particle reinforeced metal matrix composites(PRMMCs) increases with reducing thickness or/and enhancing bond strength of interface;while it is opposite for interfacial damping.When the interface volume is contained in the reinforcements, the interface damping is high for the thick and weak-bonded interfaces,while it is low for the thick and strong-bonded interfaces.When the interface volume is not contained in the reinforcements,the Young's modulus is high for the thin and weak-bonded interfaces,while it is low for the thick and strong-bonded interfaces.(4) The volume fraction of SiC particle can be increased in order to simultaneously improve the Young's modulus and interfacial damping of SiCr_P/Al composites.It's more available to increase infiltration among reinforcement and matrix when interface is thinner.The theoretical studies can provide scientific foundation for preparation of particle reinforced metal matrix composites in practice.