Influence of non-reactive particles on the microstructure of NiAl and NiAl-ZrO2 processed by thermal explosion

Nickel aluminide intermetallic alloy and NiAl-ZrO2 composites were synthesized in a hot press by sintering reaction and thermal explosion (or Self-propagating High temperature Synthesis, SHS). The addition of a post-SHS heat treatment allows a control of the microstructure and an enhancement of the mechanical characteristics. Thus, NiAl properties processed by self-combustion are above those obtained by reactive sintering (RS). For all these syntheses, the role played by the non-reactive particles is determining. Indeed, the product granulometry is a function of the diluent size distribution since this latter acts as nucleation sites during the reactive processes. These particles can also enhance mechanical properties by specific reinforcement mechanisms and exercise an influence on SHS reaction parameters by controlling its reactivity and the thermal exchanges during self-combustion.