PROCESSING AND CHARACTERIZATION OF ALUMINUM-BASED MMCS PRODUCED BY GAS-PRESSURE INFILTRATION

A device has been designed and built for unidirectional infiltration o f ceramic preforms with a molten metal. It allows production of Al or Mg alloys reinforced with short or continuous ceramic fibres. The appa ratus has been tested for different alloys and preforms by varying the process parameters (infiltration pressure, fibre content, melt superh eat, preform preheat and solidification speed). As an example, full in filtration of Al2O3-SAFFIL chopped preforms with an Al-4wt.%Cu-1wt.%Mg -0.5wt.%Ag alloy has been achieved under controlled conditions by usin g a gas pressure between 1 and 3 MPa. The resulting metal matrix compo site has been characterised by microscopical observations and mechanic al tests. Measurements of Young's modulus, density, microhardness and mechanical loss show that the optimal process conditions for Al-4wt.%C u-1wt.%Mg-0.5wt.%Ag-SAFFIL composites are a temperature of 750 degrees C for both preform and melt and the maximum infiltration pressure of 3 MPa. Preliminary tests have shown that the gas pressure infiltration apparatus is also suitable to produce continuous fibre reinforced and hybrid metal matrix composites. (C) 1998 Elsevier Science S.A. All ri ghts reserved.