INTERFACES IN AS-EXTRUDED XD AL TIC AND AL/TIB2 METAL-MATRIX COMPOSITES/

A detailed study was conducted of the microstructure and particle-matr ix interfaces in Al/TiC(p) metal matrix composites prepared by the XD process and subsequent extrusion. A study of the morphology of the TiC particles showed that the surfaces are low index (111) and (200) plan es, the former being more common. Direct contact on an atomic scale is established between Al and TiC, allowing chemical bonds to form. Youn g's modulus is in the range expected for a composite of Al and TiC wit h good interfacial bonding and load transfer to the particles. No thir d element has been detected at the interfaces, showing that they are c lean. Both incoherent and semicoherent interfaces are seen. The interf ace character depends on the size of the particles and their orientati on with respect to the neighboring Al grains. ''Special'' interfaces w ith evidence for nearly periodic dislocations were observed in both XD Al/TiC and Al/TiB2 composites, indicating the general tendency of in situ composites to lower their interfacial energy by forming such boun daries.