INTERFACES IN AL-TIC COMPOSITES PREPARED BY INSITU PROCESSING

The interfaces occurring in metal matrix composites prepared by in-sit u processes can be atomically clean without interfering phases often s een when the composites are prepared by a mechanical mixing route. Cle an interfaces may lead to higher toughness and modulus than with conta minated interfaces. The present paper describes the interfaces in an A l matrix - TiC particulate composite prepared by exothermic reaction o f Ti and C in liquid Al (XD process). The TiC particles frequently hav e densely packed {111} planes parallel to the interface ensuring stron g chemical bond with Al. A number of Al - TiC interfaces were semicohe rent in the cast and extruded composite and the fraction of such bound aries increased with recrystallization because Al subgrains nucleated at the particles with special orientations. The composite interfaces h ave high toughness which is attributed to the partial metallic nature of bonding.