Formation of aluminum and titanium carbides was observed in Af-Ti mechanical alloys prepared with stearic acid as process control agent. Thermal analysis showed that Al4C3 forms as a result of carbon contamination together with Al3Ti phases, which react at similar to 900 degrees C to form TiC1-x and Al melt. This transition causes a previously unexplained equilibrium transition. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.