Corrosion and wear behaviour of rice husk ash - Alumina reinforced Al-Mg-Si alloy matrix hybrid composites

The corrosion and wear behaviour Al-Mg-Si alloy matrix hybrid composites developed with the use of rice husk ash (RHA) and alumina as reinforcements has been investigated. Alumina added with 2, 3, and 4 wt.% RHA were utilized to prepare 10 wt.% of the reinforcing phase with Al-Mg-Si alloy as matrix using double stir casting process. Open circuit corrosion potential (OCP) and potentiodynamic polarization measurements were used to study the corrosion behaviour while coefficient of friction was used to assess the wear behaviour of the composites. The corrosion and wear mechanisms were established with the aid of scanning electron microscopy. The results show that the corrosion resistance of the single reinforced Al-Mg-Si/10 wt.% Al₂O₃ composite was superior to that of the hybrid composites in 3.5% NaCl solution, and the corrosion rates increased with increase in wt.% RHA. The increase in the population of matrix/reinforcement interface with increase in wt.% RHA in the hybrid composites was identified as the likely reason for the increase in corrosion rates observed with increase in wt.% RHA. The coefficient of friction and consequently, the wear rate of the composites were observed to increase with increase in RHA wt.%. The wear mechanism of the composites was observed to transform from predominantly abrasive wear to a combination of both adhesive and abrasive wear with increase in RHA wt.%.