SEGREGATION OF PHASES IN THE INTERFACE OF DELTA-AL2O3 FIBER-REINFORCED AL PISTON ALLOYS

The phases forming during processing in the fibre-matrix interface of the delta-Al2O3 fibre reinforced piston alloy AlSil2CuMgNi were invest igated applying TEM methods. Preferentially Si, the Q phase (AlMgSiCu) and Mg2Si were found to form at the interface. Occasionally Al3Ni, Cu Al2, Al12Fe3Si and Mg12Al17 were also detected. The matrix outside the interface consists mainly of the Si-Al eutectic. An Al3Ni phase with orthorhombic structure with lattice parameters of a = 23.3 angstrom, b = 7.44 angstrom and c = 13.79 angstrom was found at the interface. Al 2SiO5 crystals less than 10 nm in size precipitate in Si. The phase se gregation at the fibre-matrix interface is discussed with relation to wetting, adhesion and fibre-matrix reaction during composite processin g and application.