Ignition and combustion mechanisms in Mg-Al alloys via TG-DSC and ReaxFF MD simulations

Magnesium-aluminum (Mg-Al) alloys are commonly used as high-energy powder materials in solid propellants. Clarifying their ignition and combustion mechanisms is essential to guide alloy composition and particle structure design, thereby improving solid propellant combustion performance. This study utilizes TG-DSC thermal analysis and ReaxFF molecular dynamics simulations to investigate the effect of Al content and oxidation degree on chemical bonding, diffusion behavior, as well as the thermodynamic and structural properties of Mg-Al nanoparticle (MANP) in ignition and combustion. Mutual diffusion of core Mg and external oxygen atoms is critical for accelerating the ignition and combustion of MANP. During heating, the localized clustering of Al atoms enhances the outward diffusion of Mg atoms, resulting in earlier melting of core-region atoms and facilitating faster ignition of MANP. This is consistent with TG-DSC experimental results showing that the addition of Al lowers the onset temperature of the accelerated oxidation stage. MANP combustion can be divided in three stages: rapid rise, slow and stable stage. MANP with thinner oxide layers exhibit stronger diffusion intensity of core-Mg atoms and a significantly higher capacity for oxygen adsorption on the particle surface, resulting in a higher temperature rise rate and peak temperature.