Combustion synthesis of microstructurally designed green powder compacts

This paper discusses a new elemental powder compact design that promotes considerably improved densities of combustion synthesized nickel aluminide–titanium carbide composites (at 20 vol.% titanium carbide loading) without the application of external pressure. The effect of processing temperature (700 °C, 900 °C and 1164 °C) on the product porosity, microstructure homogeneity and hardness is discussed. Results are also compared to specimens produced using the conventional green compact design and processed at the same investigated temperatures. Both porosity and in-homogeneity are reduced using this new design at a processing temperature of 700 °C, and were also both found to decrease with increase in processing temperature. Moreover, Vickers hardness measurements on the specimens revealed that the new microstructural design resulted in products with significantly superior hardness compared to materials produced through conventional green compact design. Also despite the low levels of porosity of materials produced through conventional green compact design when reacted at 1164 °C, a vastly inferior hardness was still obtained owing to poor TiC distribution, in addition to poor bonding between intermetallic grains.