OPPORTUNITIES FOR NEW GRAPHITIC ALUMINUM METAL-MATRIX COMPOSITE

Nickel coated graphite particles have been incorporated into aluminium with a second particulate phase to produce graphitic aluminium metal matrix composites (GrA-Ni) with improved processing, wear, and scuffi ng resistance. Excellent wear behaviour is provided by a combination o f solid lubrication by graphite as well as high temperature strengthen ing of the matrix alloy by nickel present as Al3Ni intermetallics. App lications being developed include cylinder liners, pistons, connecting rods, various types of brakes, air diffusers and bushings. Neutral bu oyancy of two particles, one of which is lighter and the other heavier than the aluminium matrix alloy, makes this a readily sand and die ca stable material. The presence of graphite and Al3Ni intermetallics red uces the amount of ceramic particulate required to achieve the desired wear properties, with resulting improved machinability. The compositi on of the material can be tailored to the application. All these facto rs influence the finished part cost. MST/4023A.