Dry sliding friction and wear properties of Al2O3 and carbon short fibres reinforced Al-12Si alloy hybrid composites

Al2O3 and carbon short fibres reinforced Al-12Si alloy hybrid composites were fabricated by preform squeeze-infiltration route. The effects of applied load and reinforcing fibre volume fraction on dry sliding friction and wear properties of the hybrid composites were investigated at constant sliding velocity of 0.837 m/s and sliding distance of 1005 m. Worn surfaces and subsurface regions were also observed and analysed. The results show that the critical transition load from mild to severe wear of the 12 vol.% Al2O3/Al-12Si composites improved to the range between 196 and 245 from 147 to 196 N for the monolithic Al-12Si alloy. Moreover, the addition of 4 vol.% C in the 12 vol.% Al2O3/Al-12Si composites enhanced further the critical transition load to the range between 245 and 294 N. The friction coefficient of the hybrid composites containing constant 4 vol.% C increased with the increase of Al2O3 fibre volume fraction in the mild wear regime. However, there existed an optimum Al2O3 volume fraction of 12 vol.% leading to the least wear rate of the hybrid composites. The friction coefficient and wear rate of the hybrid composites containing constant 12 vol.% Al2O3 decreased with the increase of carbon fibre volume fraction. Carbon fibre was more efficient in improving wear resistance of the hybrid composites at high applied load. Analysis of worn surfaces and subsurface regions indicated that the reinforcing fibres had no significant effect on wear mechanisms of the Al-12Si alloy. When applied load is below the critical load, dominant wear mechanisms were plowing grooves and delamination. The unpeeling delamination layer was damaged and the dominant wear mechanisms shifted to severe wear when the applied load exceeds the critical load. (C) 2004 Published by Elsevier B.V.