Microstructural Evolution and Corrosion Behaviour of Al7075 Metal Matrix Composites Reinforced With Hexagonal Boron Nitride

Abstract

This investigation focuses on enhancing the corrosion resistance of Al7075 metal matrix composites through reinforcement with hexagonal boron nitride (h-BN) hard-ceramic particles. Microstructural characterisation was carried out using optical microscopy and scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDAX). The findings indicate that localised corrosion in the Al7075 matrix originates primarily at the interfaces between the matrix and h-BN particles. A significant improvement in corrosion resistance was observed with increasing reinforcement content, particularly at 9 wt.% h-BN, where the corrosion rate decreased to 2.743 mm/a. Post-solution treatment further reduced the corrosion rate to 0.8169 mm/a, demonstrating its effectiveness in enhancing durability. Overall, the results confirm that solution treatment substantially improves the corrosion resistance of Al7075/9 wt.% h-BN composites. The corrosion behaviour was systematically evaluated using Tafel polarisation in a neutral chloride medium (3.5% NaCl).