Unveiling the combustion behaviors and flame propagation mechanism of Ti-50Al alloy in oxygen-enriched environments

To enable the application of titanium-aluminum alloys in next-generation critical aero-engine components, it is essential to systematically elucidate their combustion behavior and fire-resistance mechanisms. Herein, the ignition behavior and flame propagation characteristics of Ti-Al alloy in oxygen-enriched atmospheres were investigated using the promoted ignition-combustion (PIC) test, with systematic comparisons made against typical titanium alloy. The results indicate that the Ti-Al alloy exhibits a critical ignition pressure of 0.17 MPa and a critical ignition temperature of 1076.2 K, both of which are significantly higher than those of typical titanium alloys. The apparent activation energy for ignition of the Ti-Al alloy is determined to be 133.75 kJ mol −1 , exceeding that of typical TC11 alloy (97.72 kJ mol −1 ). This difference is associated with the Al-rich oxidation response, which suppresses inward oxygen transport, together with the high thermal stability of the γ-TiAl phase. However, once ignited, the Ti-Al alloy exhibits a substantially higher combustion rate than typical titanium alloys, and the combustion rate increases exponentially with increasing oxygen pressure. This phenomenon is primarily attributed to (i) the preferential oxidation of Al, which results in greater heat release, and (ii) the formation of a relatively low-melting interfacial structure at the solid-liquid boundary, which promotes rapid spreading. These results indicate that the synergistic regulation of Al content and the α 2 /γ dual-phase microstructure plays a key role in improving fire resistance, thereby offering fundamental design principles for next-generation high-performance titanium-aluminum alloys for aero-engine applications.