Influence of the matrix microstructure on the wear resistance of alumina continuous fiber reinforced aluminum alloy composites

The solidification microstructure and wear resistant properties were investigated for alumina fiber reinforced Al alloy matrix composites. Alumina continuous fiber of 15 μm diameter was chosen to improve the wear resistance and clarify the wear mechanism. Al-7 to 27 mass%Si alloys, in which the hard Si phase was dispersed in matrix, and Al-4.5 mass%Cu, in which matrix showed age-hardening during heat treatment were used to evaluate the influence of hardness of matrix on wear resistant. Fiber reinforced composites were fabricated via the pressure infiltration process; continuous alumina fibers were placed in a graphite mold, then molten aluminum alloy was infiltrated into the fiber preforms in a vacuum to fabricate the composites specimens with the 55 vol% fiber. The pin on ring type wear resistance test was carried out under the condition of dry and air atmosphere. Wear resistant properties of fiber reinforced composites are improved about 2 to 10 times more than unreinforced alloys. Furthermore, Al-27 mass%Si hypereutectic alloy matrix composites, in which the hard primary Si particles are dispersed in eutectic matrix, shows higher wear resistance than that of hypoeutectic alloy, which consisted of primary dendritic α phase and α + Si eutectic structure. The primary Si hard phase in matrix connects the alumina continuous fibers and prevents the breakaway of fibers from the worn surface. The wear resistances are also increased by the age hardening of matrix for Al-4.5 mass%Cu and Al-7 mass%Si based alloy matrix composites.