Effect of Zr Content on the Ignition Conditions and Flame Propagation of Ti100−xZrx Alloys

Zr is a common element in titanium alloys to enhance their mechanical properties; however, its role in combustion remains unknown. This study aimed to elucidate the effects of Zr on the ignition conditions and flame propagation of Ti100−xZrx alloys via promoted ignition-combustion (PIC) tests. Results indicated that increasing Zr content (from 30 at% to 70 at%) decreased the critical oxygen pressure, ignition temperature, and burning velocity of Ti100−xZrx alloys. The reduction in ignition conditions was attributed to a decrease in ignition activation energy (from 108.37 kJ/mol to 94.26 kJ/mol) and an increase in combustion heat (from 986.34 kJ/mol to 1049.84 kJ/mol) with Zr addition. Additionally, microstructural analysis indicated that the suppression of flame propagation was attributed to Zr promoting the formation of a dense oxide layer. This hindered oxygen diffusion, thereby suppressing the heat release of oxidation reactions in the oxide zone and the peritectic reaction in the melting zone. These findings provided new insights into optimizing the composition of burn-resistant titanium alloys to inhibit combustion kinetics.