Highly Enhanced Energetic Kinetics and Reaction Mechanism Investigation of Hydrogenated Mg-Al Alloys

Magnesium-based alloy fuels and magnesium hydride (MgH₂) are promising candidates for fuels with high reactivity attracted numerous interests in energetic field. In this work, MgH₂ with both high combustion heat and reactivity is introduced into Magnesium-Aluminum (Mg-Al) alloys through solid-state hydrogen storage technology, which achieves a well assembly of Mg, Al, and MgH₂ on a micro scale. The hydrogenation of Mg-Al alloys is a surface-to-inside process, in which hydorgen (H₂) is sequentially complexed with α-Mg, Al₁₂Mg₁₇, and Al₃Mg₂. Higher content of Mg and richer metallurgical interfaces in Mg-Al alloys can contribute to a higher hydrogenation degree. In addition, distinguished from Mg-Al alloys, the oxidization of hydrogenated Mg-Al alloys is triggered by the dehydrogenation and oxidation of MgH₂ at ≈300 °C and 440 °C, promoting further oxidation of the internal Mg-Al intermetallic compound and advancing the oxidation temperature ≈10–20 °C. The multi-spectral combustion diagnostic technique further illustrates hydrogenated Mg-Al alloys show 200–400 °C higher combustion flame temperature than raw materials, which can be ascribed to the positive feedback combustion mechanism of “combustion-reduction-combustion” that promotes the energetic kinetics of Mg-Al alloy hydrides. Therefore, hydrogenated Mg-Al alloys in this work show tremendous potential as high-performance reactive fuels in energetic materials.