Advances on Stress-Altered Aluminum Particle Combustion and Improvement of Reactive Projectiles

Stress-altering aluminum (Al) particles by annealing and quenching has shown to be a promising treatment to enhance the reactivity of metal fuels, however, is not well understood. Herein, experiments led to a deeper understanding of the stressing treatment, its effects on physical properties such as surface energy, pressure generation, changes in reactivity, and potential as an alternative fuel source. While this research investigates Al stress-alteration, it also provides new insights into metal fuel particle combustion overall. Results include a novel understanding of pressure development regarding the facilitation of diffusion oxidation in a thermite, where lower peak pressures corresponded to higher thermite reactivity due to the consumption of oxygen generated when the solid oxidizer decomposed. Stress-altered Al was found to have up to 40% reduction in particle surface energy. When launched as a reactive material (RM) projectile, clear differences in system performance were observed, where higher surface energy samples resulted in more pronounced blast waves. RM projectiles were then studied to improve survivability, as they tend to disintegrate upon launch, while also enhancing energy release in a high velocity impact ignition system. When RM projectiles undergo an annealing treatment with 1-2 wt.% silica additive, survivability was achieved, and energy release was enhanced by way of increased fragmentation. Annealing was shown to provide RM ductility though dislocation recovery in the aluminum matrix. In contrast, silica lowered the material’s yield strength and toughness, and recovery was inhibited in dislocations surrounding inclusionary sites. These findings further the research of stress-altered Al and it’s potential as a viable fuel source in specific applications like propellants and pyrotechnics.

Embargo status: Restricted until 01/2028. To request the author grant access, click on the PDF link to the left.