Mechanical and wear behavior of an Al/Si alloy metal-matrix composite reinforced with aluminosilicate fiber

Aluminum/silicon alloys reinforced with low volume fractions of short aluminosilicate fibers were prepared by the squeeze-casting process. The wear behavior of the metal-matrix composites (MMCs) and that of the monolithic Al/12 wt% Si alloy was investigated in pin-on-disk tests from room temperature to 400°C under dry conditions. It was found that the additions of 3-7 vol. % of fiber conferred a beneficial effect in reducing the wear rate of the alloy at room temperature. Furthermore, the results of investigations at room, temperature also indicated that the MMC with 4·5% fiber exhibited the lowest value of the coefficient of friction. Sliding wear tests at high temperatures revealed that the wear rates of the MMCs were significantly lower than those for the unreinforced alloy, particularly above 300°C. The worn surfaces and subsurfaces of specimens tested at high temperatures were examined by scanning electron microscopy (SEM). SEM observations revealed that extensive microcracking occurs on the surface of the monolithic alloy tested at lower loads. The growth of these microcracks eventually led to the delamination of debris from the alloy surface. The aluminosilicate fibers tended to reduce the extent of plastic deformation in the surface layer, thereby reducing the occurrence of microcracking in the MMCs. © 1996 Elsevier Science Limited.