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| Title: |
Twin boundary spacing effects on shock response and spall behaviors of hierarchically nanotwinned fcc metals |
| First author: |
Yuan Fuping;Chen Liu;Jiang Ping;Wu Xiaole |
| Abstract: |
Atomistic deformation mechanisms of hierarchically nano-twinned (NT) Ag under shock conditions have been investigated using a series of large-scale molecular dynamics simulations. For the same grain size d and the same spacing of primary twins λ 1 , the average flow stress behind the shock front in hierarchically NT Ag first increases with decreasing spacing of secondary twins λ 2 , achieving a maximum at a critical λ 2 , and then drops as λ 2 decreases further. Above the critical λ 2 , the deformation mechanisms are dominated by three type strengthening mechanisms: (a) partial dislocations emitted from grain boundaries (GBs) travel across other boundaries; (b) partial dislocations emitted from twin boundaries (TBs) travel across other TBs; (c) formation of tertiary twins. Below the critical λ 2 , the deformation mechanism are dominated by two softening mechanisms: (a) detwinning of secondary twins; (b) formation of new grains by cross slip of partial dislocations. Moreover, the twin-free nanocrystalline (NC) Ag is found to have lower average flow stress behind the shock front than those of all hierarchically NT Ag samples except the one with the smallest λ 2 of 0.71 nm. No apparent correlation between the spall strength and λ 2 is observed in hierarchically NT Ag, since voids always nucleate at both GBs and boundaries of the primary twins. However, twin-free NC Ag is found to have higher spall strength than hierarchically NT Ag. Voids can only nucleate from GBs for twin-free NC Ag, therefore, twin-free NC Ag has less nucleation sources along the shock direction when compared to hierarchically NT Ag, which requiring higher tensile stress to create spallation. These findings should contribute to the understandings of deformation mechanisms of hierarchically NT fcc metals under extreme deformation conditions.
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| Contact the author: |
Yuan Fuping |
| Page number: |
063509/1-063509/11 |
| Issue: |
6 |
| Subject: |
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| Authors units: |
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| PubYear: |
2014 |
| Volume: |
115 |
| Unit code: |
115111 |
| Publication name: |
JOURNAL OF APPLIED PHYSICS |
| The full text link: |
http://dx.doi.org/10.1063/1.4865738 |
| Full papers: |
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| Departmens of first author: |
LNM |
| Paper source: |
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| Paper type: |
AK |
| Participation of the author: |
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| ISSN: |
0021-8979 |
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