High temperature friction and wear behaviour of Al2O3 and/or carbon short fibre reinforced Al–12Si alloy composites

Al2O3 and/or carbon short fibre reinforced Al–12Si alloy composites were prepared by preform squeeze-infiltration route. High temperature friction and wear properties of the composites were investigated at a constant sliding velocity of 1.57 m/s and load of 50 N as well as a sliding distance of 942 m. Worn surfaces and subsurface regions were also analysed. The results show that the hybrid composites reinforced with Al2O3 and carbon fibres attained superior wear resistance over the entire range of test temperatures. The critical transition temperature from mild wear to severe wear of the composites reinforced with only 12 vol.% Al2O3 fibre improved to the range between 250–300 and 150–200 °C for the monolithic aluminium alloy. The critical transition temperature of the hybrid composites reinforced with Al2O3 and carbon fibres improved further to the range between 350 and 400 °C. The friction coefficient of the hybrid composites containing fixed 4 vol.% C increased with Al2O3 fibre volume fraction up to 20 vol.% except at 300 °C from 4 to 12 vol.% Al2O3. However, there existed critical range of Al2O3 fibre volume fraction leading to improved wear resistance of the hybrid composites. The friction coefficient and wear rate of the hybrid composites containing fixed 12 vol.% Al2O3 decreased with the increase of carbon fibre volume fraction up to 6 vol.%. Analysis of worn surfaces and subsurface regions indicated that the reinforcing fibres have no significant effect on wear mechanisms of Al–12Si alloy. The dominant mechanisms were cutting grooves and delamination as well as slight adhesion in the mild wear regime. The dominant wear mechanisms shifted to severe adhesion at test temperatures above the critical transition temperature.