While aluminum casing materials provide some enhanced performance and thermal loading to explosive ordinance, their overall effectiveness is highly limited by incomplete combustion and long residence times. In order to reduce these problems, the casing material must be designed to facilitate rapid fragmentation through either specialized casing geometries or greatly refined initial particle sizes. While these solutions do show some promise, they are often expensive to implement and only serve to work around the basic problem: aluminum casings have poor combustion properties at the short, microsecond time scales necessary for effective enhanced blast loadings. We propose to use multicomponent metal alloys/composites comprised of aluminum, lithium, and/or magnesium to yield a fully metallic, self-fragmenting structural material with enhanced combustion performance. Lithium and magnesium have very high volatilities (i.e., low boiling points), which cause rapid intraparticle boiling within aluminum alloy/composite particles during initial high-rate heating and combustion. The gas within the particle cannot readily escape, causing a sudden self-shattering or microexplosion of the alloy/composite fuel particle. This microexplosive process should yield microsecond-scale residence times and ultra-high combustion efficiencies when subject to the high stresses, pressures, and temperatures of an explosive shock, potentially making them ideal for enhanced blast casing materials.
