Solid state reactions in the Al-MoO3 system for the synthesis of Al2O3-Mo aluminide composites

Ceramic matrix composites reinforced with metallic particles exhibit good mechanical properties. One research line has involved the fabrication of 3A (alumina-aluminide alloys) composites via in situ consolidation of aluminum reactive powders mixed with a metallic oxide. In this paper the solid state reactions for the Al-MoO3 system and the effect of the precursor compositions for obtaining Al2O3 composites and intermetallic aluminides are studied. The reactions in vacuum for the 25 degree centigree to 750 degree centigree temperature range, and the microstructural evolution up to 1200 degree centigree studied. DTA-TG and DSG were used to determine that a heating rate of 1 degree centigree /min at the critical range of 500-600 degree centigree, resulted in controlled aluminothermic reactions. XRD and SEM showed that in the sintered composites a microstructure composed of an Al2O3 matrix and a Mo aluminide/metallic Mo dispersed phase was present. The precursor composition affects the dispersed phase in the composite (Mo aluminides and/or metallic Mo) the relative Al2O3/second phase quantities, and the hardness of the composite sintered at 1450 degree centigree. (Author) 15 refs