FORMATION OF ALUMINA-CHROMIA-CHROMIUM COMPOSITES BY A PARTIAL REDUCTION REACTION

Metal-ceramic matrix composites were formed by the partial reduction o f Al2O3-Cr2O3 solid solutions to form Cr metal particles in an Al2O3-C r2O3 matrix which had a lower Cr2O3 concentration. In Al2O3-Cr2O3 soli d solutions containing 10 and 25 wt.% Cr2O3, the microstructures produ ced by reduction are different from that expected from simple models o f internal reduction or oxide scale formation. Grain boundary diffusio n of individual grains. Small Cr particles were then observed to coars en along some, but not all, grain boundaries by concomitant process kn own as 'discontinuous coarsening'. The mechanisms controlling microstr uctural evolution in this system were examined.