TY - JOUR
T1 - The Formation and Evolution of Defects in Nanocrystalline Fe During Indentation
T2 - The Role of Twins in Pop-Ins
AU - Kuhr, Bryan R.
AU - Aifantis, Katerina E.
N1 - Funding Information:
The authors are grateful for the support of the U.S. Department of Energy’s Basic Energy Science program under grant DE-SC0017715, which made this work possible.
Publisher Copyright:
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2019/5
Y1 - 2019/5
N2 - Nanoindentation is a most common experimental tool used for obtaining information on the mechanical behavior of materials. This is done by qualitatively relating the occurrence of pop-ins (in the load–displacement plots) to microstructural changes such as dislocation formation, fracture of surface oxides, or slip transmission. The present study takes a first approach in directly verifying the micro-plasticity processes that give rise to such pop-ins by performing molecular dynamics indentation simulations in BCC Fe-nanocrystals with a Σ5 symmetric tilt boundary. The simulations allow to track the material behavior throughout the indentation process, and illustrate that each pop-in is related to twin formation, twin growth, de-twinning, dislocation nucleation and glide, or dislocation–grain boundary interactions. For the particular Σ5 boundary considered, it is found that the pop-ins are most closely associated with twin formation. Although pop-ins have been related to dislocation nucleation, a direct correlation between twinning and pop-ins has not been shown before. Adding C segregants to the Fe sample, reduced the formation of twins after initial yielding, and allowed for dislocation activity to become the more dominant deformation mechanism.
AB - Nanoindentation is a most common experimental tool used for obtaining information on the mechanical behavior of materials. This is done by qualitatively relating the occurrence of pop-ins (in the load–displacement plots) to microstructural changes such as dislocation formation, fracture of surface oxides, or slip transmission. The present study takes a first approach in directly verifying the micro-plasticity processes that give rise to such pop-ins by performing molecular dynamics indentation simulations in BCC Fe-nanocrystals with a Σ5 symmetric tilt boundary. The simulations allow to track the material behavior throughout the indentation process, and illustrate that each pop-in is related to twin formation, twin growth, de-twinning, dislocation nucleation and glide, or dislocation–grain boundary interactions. For the particular Σ5 boundary considered, it is found that the pop-ins are most closely associated with twin formation. Although pop-ins have been related to dislocation nucleation, a direct correlation between twinning and pop-ins has not been shown before. Adding C segregants to the Fe sample, reduced the formation of twins after initial yielding, and allowed for dislocation activity to become the more dominant deformation mechanism.
KW - dislocations
KW - iron
KW - nanoindentation
KW - pop-ins
KW - twins
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U2 - 10.1002/pssb.201800370
DO - 10.1002/pssb.201800370
M3 - Article
AN - SCOPUS:85056138455
SN - 0370-1972
VL - 256
JO - Physica Status Solidi (B) Basic Research
JF - Physica Status Solidi (B) Basic Research
IS - 5
M1 - 1800370
ER -