Multiple-shocks induced nanocrystallization in iron

We found that multiple shots of femtosecond laser-driven shock pulses changed coarse crystalline iron grains with a size of 140 μm into nanocrystals with a high density of dislocations, which had never been observed in conventional shock processes. We performed metallurgical microstructure observati...

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Veröffentlicht in:Applied physics letters 2014-07, Vol.105 (2)
Hauptverfasser: Matsuda, Tomoki, Sano, Tomokazu, Arakawa, Kazuto, Hirose, Akio
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Sprache:eng
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Zusammenfassung:We found that multiple shots of femtosecond laser-driven shock pulses changed coarse crystalline iron grains with a size of 140 μm into nanocrystals with a high density of dislocations, which had never been observed in conventional shock processes. We performed metallurgical microstructure observations using transmission electron microscopy (TEM) and hardness measurements using nanoindentation on cross-sections of shocked iron. TEM images showed that grains with sizes from 10 nm through 1 μm exist within 2 μm of the surface, where the dislocation density reached 2 × 1015 m−2. Results of the hardness measurements showed a significant increase in hardness in the nanocrystallized region. We suggest that the formation of a high density of dislocations, which is produced by a single shock, induces local three-dimensional pile-up by the multiple-shocks, which causes grain refinement at the nanoscale.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4890389