Desalegn Wogaso (PhD)Daniel Mekasha2024-09-032024-09-032024-06https://etd.aau.edu.et/handle/123456789/3451In recent days, monolithic metals and conventional alloys are being replaced by aluminum metal matrix composites in many applications in the field of automotive and aerospace due to a high strength-to-weight ratio, fracture limit, toughness, wear, and sustaining properties at higher temperatures. This investigation thus deals with the fabrication of aluminum metal matrix hybrid composites by stir casting technique with reinforcement of TiB2 and Gr in varying percentages through the stir casting process. Reinforcements are added in 10% TiB2 and 0%, 2%, 4%, 6%, and 8% in volume percentage of graphite particulate into Al 6061 for composite preparation. The wear and hardness properties of the hybrid composite material were studied and a microstructural examination was presented. The wear performance of the specimens was measured using the pin-on-disc technique and optimization of process parameters was conducted according to the DOE and optimized by Taguchi analysis. The results showed that the reinforcements twinned and measuring only a few μm in size, were embedded in the aluminum matrix, having an equiaxed grain structure. By the addition of 2% of graphite reinforcement, the microhardness value was drastically improved by 45.6%, from 23.2 to 33.8HV. From Sample 2 to Sample 6, the hardness increased gradually. The Maximum hardness value for this experiment, 43.43HV, was obtained in 10% reinforcement composition to give a total of 86.59% improvement in hardness. The COF from the pin-on-disk test also showed a 20.52% decrement, from 0.54 to 0.38um, at 10% composition of Gr particle because of its lubricating characteristics. The wear rate of composites reinforced with 8% graphite and 10% graphite declined by 83.18% and 85.77%, respectively, showing that the wear rate also decreases as graphite composition increases. The optimum parametric condition for COF and wear rate was achieved when the combination of factors is at a Load of 30N, at a Speed of 200RPM, and for 10 minutes with confirmation of test also supporting the conclusion with a 10.11% and 7.37%, respectively, deviation from the predicted value.en-USHybrid CompositeGraphiteWear PropertyWear ParametersStir CastingTitanium DiborideMMCsAl-6061TaguchiThesis