Combustion synthesis of Co-Al and Ni-Al systems under reduced gravity

Combustion synthesis of Ni-Al and Co-Al powder mixtures was investigated to determine the effect of gravity on the reaction process and the resultant microstructure and composition. Low gravity levels were found to play a significant role when liquid phases are present across the propagating reaction front. Experiments were conducted on binary systems, containing Al. that require the presence of the liquid phase for starting the propagating process. Temperature profile measurements were made by a two color pyrometer while qualitative observations of the whole phenomenon were extracted from video pictures obtained by a digital TV camera. The analysis and comparison (microgravity vs ground conditions) of the results indicate that the reaction temperatures are higher when operating under microgravity conditions and this change can be considered the main effect that yields improvement in the homogeneity of product microstructure. (c) 2005 Elsevier Ltd. All lights reserved