Preferential void formation at crystallographically ordered grain boundaries in nanotwinned copper thin films

Nanocrystalline materials are expected to have improved radiation resistance as the high density of grain boundary area is thought to act as an effective sink for radiation-induced defects. However, continued absorption of defects can alter the structure of grain boundaries and/or enhance their mobi...

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Bibliographic Details
Published in:Acta materialia 2015-09, Vol.96 (C), p.284-291
Main Authors: LaGrange, Thomas, Arakawa, Kazuto, Yasuda, Hidehiro, Kumar, Mukul
Format: Article
Language:English
Subjects:
Boundaries
Coarsening
DENSITY
Grain boundaries
Grain boundary migration
Grain boundary networks
Grains
High density
Low energy
Microstructure
MICROSTRUCTURES
Radiation defects
THIN FILMS
Triple junctions
TWINNING MECHANISMS
VOIDS
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Summary:Nanocrystalline materials are expected to have improved radiation resistance as the high density of grain boundary area is thought to act as an effective sink for radiation-induced defects. However, continued absorption of defects can alter the structure of grain boundaries and/or enhance their mobility, eventually leading to microstructural degradation in the form of grain coarsening, thus negating their initial radiation tolerance. Hence, an ideal microstructure might be one with a mix of boundaries that are effective sinks and limit grain coarsening. We show through in situ electron irradiation experiments, however, that this is an insufficient condition. Our observations indicate that even a high density of low energy coherent twin boundaries, supposedly stabilizing the microstructure against grain coarsening, can be a detriment in that it biases the mobility of vacancies accumulating during irradiation thereby resulting in preferential void nucleation near twin boundaries. These observations highlight the fact that radiation induced grain boundary migration depends greatly on the topology of the grain boundary network and that the migration of high-angle grain boundaries can be hindered when coordinated at triple junctions composed of at least two low-energy boundaries, e.g., coincidence site lattice boundaries.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2015.06.015