Mechanical Properties and Corrosion Behavior of CeO₂ and SiC Incorporated Al5083 Alloy Surface Composites

In this investigation, nano-sized cerium oxide (CeO₂) and silicon carbide (SiC) particles were stirred and mixed into the surface of an Al5083 alloy rolled plate using friction stir processing (FSP) to form a surface nano-composite layer. For this purpose, various volume ratios of the reinforcements either separately or in the combined form were packed into a pre-machined groove on the surface of the plate. Microstructural features, mechanical properties, and corrosion behavior of the resultant surface composites were determined. Microstructural analysis, optical microscopy and scanning electron microscopy, showed that reinforcement particles were fairly dispersed inside the stir zone and grain refinement was gained. Compared with the base alloy, all of the FSP composites showed higher hardness and tensile strength values with the maximum being obtained for the composite containing 100% SiC particles, i.e., Al5083/SiC. The corrosion behavior of the samples was studied by conducting potentiodynamic polarization tests and assessed in terms of corrosion potential, pitting potential, and passivation range. The result shows a significant increase in corrosion resistance of the base alloy; i.e., the longest passivation range when CeO₂ alone was incorporated into the surface by acting as cathodic inhibitors. Composites reinforced with SiC particles exhibited lower pitting resistance due to the formation of microgalvanic couples between cathodic SiC particles and anodic aluminum matrix. The study was aimed to fabricate metal matrix surface composites with improved hardness, tensile strength, and corrosion resistance by the incorporation of CeO₂ and SiC reinforcement particles into the surface of Al5083 base alloy. Optimum mechanical properties and corrosion resistance were obtained for the FSP composite Al5083/(75%CeO₂ + 25%SiC). In this particular FSP composite, hardness and tensile strength were increased by 30, and 14%, respectively, and passivation range was increased to 0.19 V/SCE compared to the base alloy with no passivation range.