Effect of Al<inf>2</inf>O<inf>3</inf> coating thickness on microstructural characterization and mechanical properties of continuous carbon fiber reinforced aluminum matrix composites

Continuous carbon fiber (CF) reinforced aluminum (Al) matrix composites have become a potential lightweight material in aerospace and commercial applications. In this work, the alumina (Al2O3) coating was uniformly synthesized on the surface of CF by the sol-gel method for improving the wettability and reducing the interfacial reaction between molten Al alloy and CF, while the Al2O3-coated CF was subsequently used to fabricate CF/Al composites via pressure infiltration technique. Effects of heat treatment temperature, immersion time, and immersion-drying cycle on the surface morphologies and mechanical properties of Al2O3-coated CF were studied, and the influences of the coating thickness on the infiltration quality and the mechanical properties of composites were also investigated by means of the microstructural analysis, interfacial characterizations and tensile property tests. The results show that the Al2O3-coated CF with excellent integrity and mechanical properties was obtained at 500 °C for 2 immersion-drying cycles by the immersion time of 5 min per cycle. The Al2O3 coating can effectively improve pressure infiltration quality and mechanical properties based on the suitable interfacial bonding strength and good wettability. The optimized Al2O3 coating thickness is 100 nm for better improving the mechanical properties of CF/Al composites.