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Title: 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 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 × 10{sup 15 }m{sup −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.
Authors:
;  [1] ;  [1] ;  [2] ;  [3] ;  [2]
  1. Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)
  2. (Japan)
  3. JST, CREST, Suita, Osaka 565-0871 (Japan)
Publication Date:
OSTI Identifier:
22311071
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CROSS SECTIONS; DISLOCATIONS; GRAIN REFINEMENT; HARDNESS; IRON; LASER RADIATION; MICROSTRUCTURE; NANOSTRUCTURES; SURFACES; THREE-DIMENSIONAL CALCULATIONS; TRANSMISSION ELECTRON MICROSCOPY