A study of self-propagating high-temperature synthesis of NiAl in thermal explosion mode

Processing of NiAl in the thermal explosion mode of Self-propagating High-temperature Synthesis (SHS) was investigated at different heating rates varying between 5 and 60 degreesC/min. Three different Ni particle sizes were used and experiments were conducted in vacuum and argon atmospheres to arrive at an optimized processing window. On-line videography of the process provided the visual evidence of the different stages of thermal explosion. Evolution of the process was studied by on-line thermometry, optical and scanning electron microscopy, XRD and mercury intrusion porosimetry. The results showed that the combustion behaviour was independent of the atmosphere but strongly dependent on the rate of heating and hence on the extent of pre-combustion reaction. Process modelling was carried out to describe the effect of the rate of heating both on the pre-combustion reaction and the combustion in the case of thermal explosion. This model could successfully rationalize the experimental results. (C) 2002 Acta Materialia lnc. Published by Elsevier Science Ltd. All rights reserved.