Atomistic elucidation of micro-explosion combustion mechanism in Al-Li alloys

Al-Li alloys represent a promising class of additives for advanced energy and propellant systems, owing to their unique micro-explosion combustion mode and enhanced performance. This study employs molecular dynamics simulations to illuminate the micro-explosion behavior of Al-Li alloys from an atomistic perspective. Key processes in Al-Li alloy combustion upon laser heating, such as melting behavior, heat transfer, mass diffusion, and product flows, are investigated in the case of alloy-AP interface. The numerical results reveal that the reduced ignition delay of Al-Li alloys, as observed in experimental studies, is primarily attributed to Li doping, which promotes moderate interface combustion before the onset of melting. Upon melting, Li atoms diffuse toward the AP oxidizer and eventually eject into the gas-phase environment and trigger micro-explosion combustion. Notably, only Li atoms located on the substrate surface actively contribute to triggering the micro-explosion, while those in the interior of substrate remain confined. Furthermore, the formation of LiCl provides an efficient reaction pathway to neutralize Cl atoms, drastically reducing HCl emissions and enabling environmentally friendly combustion. The Al-Li alloys undergo complete combustion, resulting in superior propulsion capabilities, and exceptional overall performance compared to the case with neat Al. These pivotal numerical findings offer groundbreaking insights into the micro-explosion dynamics of Al-Li alloys, laying a robust atomistic foundation for the advanced structural design and optimization of high-performance solid propellants.