Reactive fragment materials made from an aluminum–silicon eutectic powder

We explore the use of an aluminum–silicon eutectic powder to produce reactive materials that fragment and combust following high-velocity impact. Unlike the pure aluminum powders traditionally used in these materials, the eutectic sinters readily and has a reduced melting point. This allows the tensile strength/ductility and fracture toughness to be tuned with partial sintering; increases in these properties, however, generally result in a reduction in combustion energy release on impact. Three heat treatments were studied for isostatically compressed aluminum–silicon materials, and two baseline pure aluminum materials using fine and coarse powders were also fabricated for comparison. Mechanical measurements and impact calorimetry tests showed that partial sintering at the nominal melting point increases tensile strength and toughness by approximately 350% but does reduce combustion energy output; however, the reduction is only prominent above 1300 m/s for the conditions studied here. Below this point, the partially sintered Al–Si has similar impact-induced combustion as an extremely brittle, unannealed pressed Al powder. Pure aluminum and alloy materials with similar mechanical properties and starting particle size show comparable combustion energy release, suggesting that powder size and fragmentation properties are more important than the variation in melt point.