Temperature-Resolved Combustion Behavior of Ammonium Perchlorate Compositions Containing Secondary Al-Si Alloy Powder

This study investigates the combustion behavior, composition-dependentl,3 combustion regimes, and temperature–time characteristics of ammonium perchlorate (AP)-based energetic compositions containing commercial aluminum (Al) and secondary Al-Si alloy powders. The secondary Al-Si powder was obtained from recycled automobile pistons and contained 75.42 wt.% Al and 10.74 wt.% Si, while the commercial Al powder contained 98.02 wt.% Al. Particle-size analysis showed similar median particle sizes for the commercial Al and secondary Al-Si powders, with D50 values of 4.429 and 4.527 μm, respectively. However, the secondary Al-Si powder exhibited a substantially broader particle-size distribution, with D10, D90, and Span values of 0.878 μm, 49.260 μm, and 10.687, respectively, compared with 3.833 μm, 5.484 μm, and 0.373 for commercial Al. Microscopic observations showed that the secondary Al-Si powder consisted predominantly of irregular and angular particles with a more heterogeneous surface morphology. AP/metal mass ratios of 60:40, 65:35, 70:30, and 75:25 were investigated. At 60:40, both compositions exhibited rapid and intense combustion, whereas at 65:35, both systems showed stable self-propagating combustion. At 70:30, the AP + Al composition exhibited intermittent combustion, while the AP + Al-Si composition maintained stable self-propagating combustion. At 75:25, both systems showed interrupted combustion. All combustion experiments were performed in triplicate, and the results are reported as mean ± standard deviation. Temperature–time profiles were obtained for all investigated AP/metal ratios, revealing distinct continuous and intermittent thermal responses corresponding to the observed combustion regimes. At 65:35, the maximum local apparent temperature reached 2552.9 ± 23.8 °C for AP + Al-Si and 1865.4 ± 19.7 °C for AP + Al. The results demonstrate that replacing commercial Al with secondary Al-Si alloy powder changes the observed combustion regimes and temperature–time response of AP-based compositions under the investigated conditions. These differences are associated with the combined effects of particle-size distribution, morphology, chemical composition, and phase composition rather than with a single material parameter.