Processing and Properties of Alumina‐Graphite Platelet Composites

Fine‐grain Al 2 O 3 ‐graphite platelet composites have been fabricated by both filter pressing and tape casting with up to 50 vol% of fine or coarse graphite flakes. Filter pressing behavior remains unchanged with coarse graphite flake additions. Strength of hot‐pressed specimens decreases from about 350 to about 50 MPa with 50 vol% graphite. Preliminary experiments indicate that platelet orientation has a significant effect on strength: Platelets oriented perpendicular to the fracture plane and face‐on to the crack front are about 20% weaker than composites with platelets oriented both perpendicular to the fracture plane and edge‐on to the crack front. This suggests that the flakes behave as oriented voids in the microstructure.