Preparation and properties of pressureless infiltrated SiC and AlN particulate reinforced metal ceramic composites based on bronze and iron alloys

Metal ceramic composites were prepared from SiC and G–CuAl10Ni, AlN and G–CuAl10Ni, as well as AlN and GGG–NiSiCr 35 5 2 by a pressureless melt infiltration process starting from porous ceramic preforms and the mentioned alloys. Titanium was used to improve wetting of the ceramic materials by the liquid metals. The microstructure and mechanical properties (density, Youngʹs modulus, bending strength and fracture toughness) were characterised and prototypic parts prepared. With increasing SiC particle size, the amount of metal in the matrix of the SiC containing composites increases. A correlation between the microstructure and the mechanical properties was observed. The matrix of the AlN containing composites consists mainly of the residual alloy, whereas the matrix of the SiC containing composites contains also silicides, which were formed during the infiltration process. A comparison between preforms consisting either of milled AlN powder or porous AlN granulate and their infiltration with GGG–NiSiCr 35 5 2 shows, that the decomposition of granulate hinders further infiltration in these preforms. The deformation behaviour of the materials, obtained from bending strength measurements, indicates a failure tolerant behaviour for composites with a high amount of metal in the matrix.