Study On Damping Behavior Of Particulates Reinforced Al Matrix Composites Fabricated By Spray Atomization And Codeposition

With the expending applications of metal matrix composites (MMCs), there is growing demand for their damping capacity. In this dissertation, the damping behavior of Al alloy based MMCs fabricated by spray atomization and codeposition with different heat treatment processing was studied systematically.The courses of ageing precipitation of 6013A1(6061A1, 6066Al)/SiCp MMC were accelerated, owing to the microstructure features resulted from rapid solidification in spray codeposition as well as the increased dislocation density in the matrix reinforced by silicon carbide particles.The damping behaviors of 6000 series Al alloys/SiCp MMC with different heat treatments was investigated systematically by means of changing the quench medium after solution treatment. The damping capacity of all the treated samples were tested using a multifunctional internal friction instrument and DMA, and the spectra showing the dependence of internal friction upon frequency, temperature and strain amplitude were obtained. As the results show, the damping capacity of different treated samples changed slightly at low temperature, but remarkably at elevated temperature. Over a 100癈 to 270 癈 temperature range, the damping capacity was ranked from great to small as follows: sample cooled in furnace, sample cooled in the air, sample quenched at -70 癈, sample without heat treatment, sample quenched at-195癈 and sample quenched in water. In addition, the damping capacity of all the specimen reached 1?10-2 when temperature was above 180癈, which exhibited excellent high temperature damping capacity. On the other hand, the modulus did not change with frequency at low temperature, while, it decreased linearly with increasing frequency above the temperature of 160癈Meanwhile, the lower the frequency was, the more modulus deterioration was observed. It was considered that the dislocation damping, the interface damping between the matrix and reinforcement particulates and the inherent internal friction of the matrix alloys andmechanisms of the peak phenomena were in good accordance with the G-L theory of dislocation internal friction.Through introducing the model for dislocation damping and setting up a relaxation model for micro-sliding of interface, the damping mechanisms for the SiCp/Gr hybrid MMC were studied. The operation mechanisms in the hybrid MMC were dislocation damping, Gr/Al interface micro gliding damping and interface internal friction at low temperature, and the interface sliding and dislocation movement dragging the point defects damping at high temperature. The damping capacity of SiCp/Gr hybrid MMC were much greater than the SiCp-reinforced MMC. It was over three times higher than that of the SiCp-reinforced MMC. It was further proposed that selecting the proper SiCp/Gr ratio could improve the damping capacity of the materials, with holding high strength and modulus.The damping capacity of SiCp-reinforced MMC was simulated dynamically by setting up a new multi-particulate interface model, under the condition of different heat treatments and actual interface stress using finite element method and experiment dada. As a result, the simulation results were in good accordance with the experiments.