Formation of nanostructured eutectic network in α-Al2O3 reinforced Al–Cu alloy matrix composite Original Research Article

We report the fabrication and characterization of an Al–Cu alloy matrix composite, which is reinforced by α-Al2O3 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 °C. 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 α-Al2O3 particles at higher temperature. When the sintered sample was cooled down from 1000 °C, 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 α-Al2O3 particles and Al(Cu)–Al2Cu eutectic, which are embedded in the Al(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.