Scientists identify unique metal formed by Hiroshima atomic bomb blast

Researchers from the University of Florence and UC Berkeley have identified a previously unknown metallic alloy that formed during the atomic bombing of Hiroshima on August 6, 1945. The material, named 'Hiroshimaite,' was discovered within microscopic glass spherules preserved in sand samples from Hiroshima Bay more than 80 years after the explosion.

The alloy consists of a tiny metallic particle approximately 10 micrometers in size, composed primarily of iron with additional elements including chromium, nickel, silicon, molybdenum, manganese, and aluminum. Analysis revealed the material possesses a unique ordered crystalline structure of the AlAu₄ type—a β-Mn variant—that had not previously been documented for materials with this chemical composition. Four independent measurements confirmed the chemical composition remained consistent throughout the particle, indicating it crystallized from a single droplet of molten metal.

The formation mechanism occurred during the extreme conditions of the nuclear blast, when temperatures in the fireball exceeded 7,000°C. This intense heat vaporized buildings, soil, metal structures, glass, concrete, and other materials in the impact zone. The resulting metal vapor mixed rapidly and then cooled so quickly that atoms solidified in an unusual arrangement, creating the metastable crystalline structure. Researchers examined 34 Hiroshimaite samples using optical and electron microscopy, electron microprobe analysis, and X-ray crystallography, identifying one particle with the novel composition and structure among predominantly known iron-chromium alloys.

The discovery demonstrates that nuclear explosions can create material phases unattainable through conventional metallurgical processes. Researchers note this parallels an earlier discovery of quasicrystals formed during the Trinity nuclear test in New Mexico in 1945, suggesting nuclear detonations constitute natural laboratories for forming non-equilibrium alloys. Scientists indicate the material cannot be classified as a high-entropy alloy in the strict sense, as its composition is heavily skewed toward iron and possesses ordered structure, unlike typical high-entropy alloys with balanced component concentrations and disordered arrangements. However, the alloy represents an intermediate class combining features of both categories.

While practical applications remain unclear, researchers suggest understanding such material-formation processes could inform development of new high-strength, lightweight, heat-resistant alloys for industrial and technological applications. The findings also indicate potential applications in nuclear forensics, enabling reconstruction of details about nuclear detonations through debris composition analysis.