Effect of grain boundary on the ignition and flame propagation mechanisms of TC11 alloy in oxygen-enriched environment

Grain boundaries (GBs) were known as a kind of common defects, but their impact on metal combustion was unclear. This study discovered that when the TC11 alloy's grain size reduced, the critical temperature and oxygen pressure for ignition dropped and the burning velocity accelerated. A modified Frank-Kamenetskii model demonstrated a well match to the relationship between grain size and ignition temperature, and the GBs showed a lower activation energy for ignition than the intragrain. The primary processes via which GBs influenced the kinetics of combustion were the peritectic reaction between Ti and O and the intergranular diffusion of alloying elements.