Production of Micro-TiB2 and Nano-SiC hybrid particle reinforced AA6XXX matrix composite materials and investigation of mechanical properties

In this master's thesis, the production and mechanical characterization of hybrid composite materials reinforced with micro-sized TiB₂ and nano-sized SiC particles within an AA6061 aluminum alloy matrix were systematically investigated. The study was conducted in two main stages. In the first stage, AA6061/TiB₂ composites containing different TiB₂ contents (0, 2.5, 5, 10, and 15 wt.%) were produced using powder metallurgy followed by hot extrusion. The powder mixtures were homogenized in a three-dimensional tumbler mixer, compacted at 200 MPa through cold pressing, and subsequently hot-extruded at the designated temperature using an extrusion ratio of 1:3. The extruded composites were characterized through microstructural examinations, density and hardness measurements, three-point bending tests, and dry sliding wear analyses to assess their mechanical and tribological performance. Based on these analyses, the AA6061/TiB₂ composition exhibiting both high extrudability and superior mechanical performance was identified. In the second stage, nano-sized SiC particles (≈40 nm) were incorporated into the optimum AA6061/TiB₂ composite matrix at weight fractions of 0.25, 0.5, 1, and 2 wt.% to produce hybrid composites. To enhance the distribution homogeneity of the nano-sized reinforcements, the powder mixtures were dispersed in ethanol and subjected to ultrasonic and magnetic stirring, followed by filtration, drying, and re-homogenization in a three-dimensional mixer. The powders were then compacted at 200 MPa and extruded at 550 °C. Due to severe agglomeration and compactability problems, the composite containing 4 wt.% nano-SiC could not be successfully fabricated and therefore was excluded from the characterization studies. Mechanical and microstructural evaluations of the hybrid composites revealed that the incorporation of nano-SiC provided a synergistic strengthening effect together with TiB₂, improving the overall performance of the AA6061-based composite system within an optimal reinforcement range. This study contributes to the development of lightweight, high-strength, and wear-resistant aluminum-based composite materials and provides valuable insights for designing advanced hybrid reinforcement strategies for engineering applications.