Formation of nanostructured eutectic network in α-Al2O3 reinforced Al-Cu alloy matrix composite

We report the fabrication and characterization of an Al-Cu alloy matrix composite, which is reinforced by alpha-Al-2-O-3 particles and nanometer-sized (nm-sized) lamellar eutectic. The composite was fabricated by sintering and rapid quenching of an Al-20wt.%CuO sample. We had performed differential thermal analysis on the sample, and found that the reaction between Al and CuO took place between 580 and 700 degreesC. Results from scanning and transmission electron microscopies indicated that amorphous Al2O3 was initially formed in the reaction. It was then crystallized and transformed to the more stable alpha-Al2O3 particles at higher temperature. When the sintered sample was cooled down from 1000 degreesC, the two-phase Al(Cu)-Al2Cu eutectic was formed. The size and the distribution of the eutectic network strongly depended on the rate of cooling. The final sintered product contains alpha-Al2O3 particles and Al(Cu)-AlCu eutectic, which are embedded in the AI(Cu) matrix. In comparison, the eutectic network in the oil-quenched sample is distributed more evenly and is finer in size, with lamellar spacing as small as 200-300 nm, than that of the furnace-cooled sample. The Vickers hardness value of the oil-quenched sample has an average of 123, which is 50% higher than that of the furnace-cooled sample. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.