INTERFACES IN METAL-MATRIX AND INTERMETALLIC-MATRIX COMPOSITES

It is well known that the nature of the interface between reinforcement and matrix has a very important role in determining the mechanical properties of composites. However, there are other unusual and important aspects of the interface. An intriguing observation concerning particulate TiB2/NiAl composites is the lack of dislocation generation after cooling from high temperature (1673 K) annealing. The predicted thermal residual stress is very large and this stress should be relieved by dislocation generation. It is possible that an interface layer exists between the TiB2 and NiAl that can act as a stress absorber. Also, in the case of continuous filament Al2O3/NiAl there can be differences in the bond strength between the filament and the matrix. Experimental and theoretical results indicate that the interface between SiC and Al is non-coherent. There is no layer at the interface between Al2O3 or TiB2 and NiAl that can act as a stress absorber. Continuous filament Al2O3/NiAl was degraded by graphite decorations at the interface. An unusual diffraction modulation was observed in the Al2O3 filament, and this could be modelled by finite element analysis.