REACTION PROCESSING OF IRON ALUMINIDES

Iron aluminides (Fe3Al and Fe3Al + 2% or 5% Cr) and aluminide matrix composites (Fe3Al + 5% Cr + 10 wt.% Al2O3) were synthesized by heating elemental powder compacts to initiate an exothermic reaction. Densification was accomplished using either hot isostatic pressing or Ceracon consolidation during the exothermic reaction, as well as Ceracon consolidation of pressureless reaction sintered preforms. The microstructures and tensile properties of these materials have been characterized. It is demonstrated that reaction processed materials exhibit significantly higher strength than material fabricated by hot extrusion of prealloyed powder owing to their refined grain size. Relationships between the processing parameters and resultant microstructures and properties have been determined. The results indicate that Ceracon consolidation of preforms that have been pre-reacted at ambient pressure yields superior homogeneity compared to in situ reaction during consolidation. This processing route is preferred when alloying additions of chromium are desired for increased ductility.