| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 103 === 6061 aluminum-based metal matrix composites (MMCs) are ideal materials for structural applications due to their high strength to weight ratio. The trace amounts of magnesium and silicon are normally added in the alloys to achieve precipitation strengthening. In this study, the Al6061 composites reinforced with Y2O3, TiC by mechanical alloying were investigated. Addition of the rare earth element-Lanthanum in Al6061 as in-situ La2O3 particles during ball milling was also further studies. Mechanical alloying is a complex process and has a large influence on the characteristics of powder materials. The result shows that the milling time, annealing temperature and different reinforcement particles have significant influence on microstructure uniformity, hardness, densification, and ductility of the materials. The results also indicate that the addition of TiC particles to the Al matrix can act as a milling agent and therefore refine the particle size during ball milling. The Si-rich phase and La-Si compound can be found in the Al6061- Y2O3 and Al6061-La samples respectively. Regarding with aging treatment of Al6061 composites, the samples were solutions heat treated at 600∘C for 2h, followed by cold water quenching, and then aging at 160∘C. The result suggested that the time to achieve peak aging decreases with increasing aging temperature. Different reinforcement particles have significant influence on formation of precipitates and hardness associated with aging time.
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