Reactions Between Aluminum Oxide and Carbon The Al 2 O 3 —Al 4 C 3 Phase Diagram

A phase diagram of the system A1 2 O 3 ‐A1 4 C 3 is proposed. Two intermediate oxycarbides, A1 4 O 4 C and A1 2 OC, were established. Eutectic melting between alumina and A1 4 O 4 C occurred at 1840° C. No other low melting was observed. The alumina phase was not corundum but was similar to delta‐alumina. Because of the high reactivity of aluminum carbide and all the intermediate compounds with moisture and oxygen, use of refractories based on the system A1 2 O 3 ‐A1 4 C 3 must be limited to applications where these agents are excluded. The behavior of high‐alumina refractories in the presence of carbon is explained.