REACTIVE SINTERING AND REACTIVE HOT ISOSTATIC COMPACTION OF ALUMINIDE MATRIX COMPOSITES

Reactive powder-processing techniques involve use of a transient liquid phase for the formation of a compound. Two variants of reactive synthesis have been successfully applied to the fabrication of aluminide matrix composites. In certain systems it is possible to react mixed elemental powders directly to form a nearly full density structure (such as Ni3Al and NbAl3). This approach is applicable to systems with sufficient adiabatic heating from the reaction exotherm to induce densification by liquid phase sintering. In systems with lower reaction enthalpies, an alternative involves the application of an external stress during the reaction. The two main variants illustrated here are hot isostatic compaction of mixed elemental powders (nickel + aluminum) or hot isostatic compaction of partially reacted powders (TiAl). From this base it is possible to identify the best processing approach based on the system thermodynamics.