Ignition mechanism in combustion synthesis of Ti-Al and Ti-Ni systems

Ignition phenomena in combustion synthesis (CS) of intermetallic compounds, Ti-Al and Ti-Ni systems, were studied. Different compositions for both systems were investigated. The experiments were performed in quasi-adiabatic conditions and carried out in thermal explosion mode. A CO2 laser was used as external energy source and was set at different powers to investigate the effect of the heating ramps on the ignition parameters. For both intermetallic systems, the ignition times show an exponential decay as a function of the specific power in use. The ignition temperatures were found to be characteristic for each system and constant at 645 +/- 5 and 930 +/- 10degreesC for Ti-Al and Ti-Ni, respectively. A numerical model was developed to estimate the ignition energy. The calculated energy values are 18 +/- 1, 19.5 +/- 1 and 22.5 +/- 1kJ/mol(at) for Ti:Al = 3:1, 1:1, 1:3, respectively, and 27 +/- 0.5 kJ/mol(at) for all the studied compositions in the Ni-Ti system. (C) 2003 Elsevier Science Ltd. All rights reserved.