Mechanical Properties and Solid Lubricant Wear Behavior of Al/Al2O3/C Hybrid Metal Matrix Composites Fabricated by Squeeze Casting Method

Abstract

In this study, mechanical properties and wear behavior of Al/Al₂O₃/C hybrid metal matrix composites fabricated by squeeze casting method was characterized. The effects of volume fraction of carbon fiber on mechanical properties of hybrid composites was investigated. Tensile strength of Al/Al₂O₃/C composites was decreased by increasing the addition of carbon fiber. The carbon fiber additions were seen to be less effective in strength than when only alumina fibers were incorporated, because carbon fibers in hybrid systems are difficult to wet by molten aluminum alloys and react with a matrix alloy to form brittle aluminum carbide (Al₄C₃). Ductility was considerably reduced by increasing the incorporation of carbon fiber. Wear behavior of Al/Al₂O₃/C composites was characterized by the dry spindle wear test under various sliding speeds. The wear resistance of Al/Al₂O₃/C composites was remarkably improved over Al/Al₂O₃ composites by adding carbon fibers to Al/Al₂O₃/C composites. Specifically, at the intermediate sliding speed the wear resistance of Al/Al₂O₃/C composites containing 8 vol.% carbon fiber was found to be better than that of the rest of the carbon hybrid composites, but amounts of carbon volume fraction were of little effect on wear resistance at high sliding speed of 3.62 m/sec. From fractographic studies, damaged sections in wear surfaces of hybrid composites at intermediate sliding speed were seldom observed due to the formation of solid lubrication film. The solid lubrication film which was formed as a result of adding carbon fibers improved the wear resistance of carbon hybrid composites because this film reduced the high friction force between MMCs and counter material. Wear model of Al/Al₂O₃/C composites was also suggested by the examination of worn surfaces.