Mechanically alloyed Al-Ti powders prepared by mechanical milling at cryogenic temperatures

New metal-based reactive materials are being developed aimed to replace aluminum as a fuel additive in propellants, explosives, and pyrotechnics. Recently, potential benefits of mechanically alloyed Al-rich Al-Ti powders were discussed in the literature; however, preparation of fine powders of such alloys could not be achieved by mechanical milling at room temperature because of ductility of the material. This paper investigates the feasibility of preparation of fine mechanically alloyed Al-rich Al-Ti powders using mechanical milling at cryogenic temperatures. Attrition milling, a readily scalable technique is used in this study. Powders initially alloyed at room temperatures are post-processed at the liquid nitrogen temperature to reduce the particle sizes. In addition, mechanically alloyed powders are prepared directly by the cryogenic milling from elemental starting materials. Particle sizes of the prepared powders are measured using low-angle laser light scattering. Morphology is studied using scanning electron microscopy. The structures and compositions of the prepared materials are examined using x-ray diffraction. Finally, combustion performance of the prepared powders is investigated and compared to that of pure Al powders with different sizes using constant volume explosion experiments. It is shown that cryogenic milling enables one to reduce the particle sizes of the Al-rich Al-Ti alloys. It is further shown that the ignition temperatures of the mechanically alloyed powders are substantially reduced compared to pure Al.