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Author |
Bahrami, F.; Hammad, M.; Fivel, M.; Huet, B.; D'Haese, C.; Ding, L.; Nysten, B.; Idrissi, H.; Raskin, J.P.; Pardoen, T. |
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Title |
Single layer graphene controlled surface and bulk indentation plasticity in copper |
Type |
A1 Journal article |
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Year  |
2021 |
Publication |
International Journal Of Plasticity |
Abbreviated Journal |
Int J Plasticity |
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Volume |
138 |
Issue |
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Pages |
102936 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The impact of graphene reinforcement on the mechanical properties of metals has been a subject of intense investigation over the last decade in surface applications to mitigate the impact of tribological loadings or for strengthening purposes when dispersed into a bulk material. Here, the effect on the plastic indentation response of a single graphene layer grown on copper is analyzed for two configurations: one with graphene at the surface, the other with graphene sandwiched under a 100 nm thick copper cap layer. Nanoindentation under both displacement and load control conditions show both earlier and shorter pop-in excursions compared to systems without graphene. Atomic force microscopy reveals much smoother pile-ups with no slip traces in the presence of a surface graphene layer. The configuration with the intercalated graphene layer appears as an ideal elementary system to address bulk hardening mechanisms by indentation testing. Transmission electron microscopy (TEM) cross-sections below indents show more diffuse and homogeneous dislocation activity in the presence of graphene. 3D dislocation dynamics simulations allow unraveling of the origin of these 3D complex phenomena and prove that the collective dislocation mechanisms are dominantly controlled by the strong back stress caused by the graphene barrier. These results provide a quantitative understanding of the impact of graphene on dislocation mechanisms for both surface and bulk applications, but with an impact that is not as large as anticipated from other studies or general literature claims. |
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Wos |
000623869800001 |
Publication Date |
2021-01-18 |
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Series Issue |
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Edition |
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ISSN |
0749-6419 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
5.702 |
Times cited |
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Open Access |
OpenAccess |
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Notes |
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Approved |
Most recent IF: 5.702 |
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Call Number |
UA @ admin @ c:irua:176729 |
Serial |
6735 |
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Author |
Wang, B.; Idrissi, H.; Galceran, M.; Colla, M.S.; Turner, S.; Hui, S.; Raskin, J.P.; Pardoen, T.; Godet, S.; Schryvers, D. |
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Title |
Advanced TEM investigation of the plasticity mechanisms in nanocrystalline freestanding palladium films with nanoscale twins |
Type |
A1 Journal article |
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Year |
2012 |
Publication |
International journal of plasticity |
Abbreviated Journal |
Int J Plasticity |
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Volume |
37 |
Issue |
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Pages |
140-156 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Nanocrystalline palladium thin films deposited by electron-beam evaporation and deformed by on-chip tensile testing reveal a surprisingly large strain hardening capacity when considering the small similar to 25 nm grain size. The as-grown films contain several coherent single and multifold twin boundaries. The coherency of the twin boundaries considerably decreases with deformation due to dislocation/twin boundary interactions. These reactions are described based on a detailed analysis of the number and the type of dislocations located at the twin boundaries using high-resolution TEM, including aberration corrected microscopy. Sessile Frank dislocations were observed at the twin/matrix interfaces, explaining the loss of the TB coherency due to the Burgers vector pointing out of the twinning plane. Grain boundary mediated processes were excluded as a mechanism dominating the plastic deformation based on the investigation of the grain size distribution as well as the crystallographic texture using Automated Crystallographic Orientation Indexation TEM. Other factors influencing the plastic deformation such as impurities and the presence of a native passivation oxide layer at the surface of the films were investigated using analytical TEM. The twin boundaries observed in the present work partly explain the high strain hardening capacity by providing both increasing resistance to dislocation motion with deformation and a source for dislocation multiplication. (C) 2012 Elsevier Ltd. All rights reserved. |
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Place of Publication |
Oxford |
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Wos |
000307416100009 |
Publication Date |
2012-05-16 |
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Edition |
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ISSN |
0749-6419; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
5.702 |
Times cited |
44 |
Open Access |
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Notes |
Iap; Fwo |
Approved |
Most recent IF: 5.702; 2012 IF: 4.356 |
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Call Number |
UA @ lucian @ c:irua:101082 |
Serial |
74 |
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Author |
Delville, R.; Malard, B.; Pilch, J.; Sittner, P.; Schryvers, D. |
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Title |
Transmission electron microscopy investigation of dislocation slip during superelastic cycling of NiTi wires |
Type |
A1 Journal article |
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Year |
2011 |
Publication |
International journal of plasticity |
Abbreviated Journal |
Int J Plasticity |
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Volume |
27 |
Issue |
2 |
Pages |
282-297 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Superelastic deformation of thin NiTi wires containing various nanograined microstructures was investigated by tensile cyclic loading with in situ evaluation of electric resistivity. Defects created by the superelastic cycling in these wires were analyzed by transmission electron microscopy. The role of dislocation slip in superelastic deformation is discussed. NiTi wires having finest microstructures (grain diameter <100 nm) are highly resistant against dislocation slip, while those with fully recrystallized microstructure and grain size exceeding 200 nm are prone to dislocation slip. The density of the observed dislocation defects increases significantly with increasing grain size. The upper plateau stress of the superelastic stressstrain curves is largely grain size independent from 10 up to 1000 nm. It is hence claimed that the HallPetch relationship fails for the stress-induced martensitic transformation in this grain size range. It is proposed that dislocation slip taking place during superelastic cycling is responsible for the accumulated irreversible strains, cyclic instability and degradation of functional properties. No residual martensite phase was found in the microstructures of superelastically cycled wires by TEM and results of the in situ electric resistance measurements during straining also indirectly suggest that none or very little martensite phase remains in the studied cycled superelastic wires after unloading. The accumulation of dislocation defects, however, does not prevent the superelasticity. It only affects the shape of the stressstrain response, makes it unstable upon cycling and changes the deformation mode from localized to homogeneous. The activity of dislocation slip during superelastic deformation of NiTi increases with increasing test temperature and ultimately destroys the superelasticity as the plateau stress approaches the yield stress for slip. Deformation twins in the austenite phase ({1 1 4} compound twins) were frequently found in cycled wires having largest grain size. It is proposed that they formed in the highly deformed B19′ martensite phase during forward loading and are retained in austenite after unloading. Such twinning would represent an additional deformation mechanism of NiTi yielding residual irrecoverable strains. |
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Corporate Author |
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Publisher |
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Place of Publication |
Oxford |
Editor |
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Wos |
000284921800007 |
Publication Date |
2010-05-17 |
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ISSN |
0749-6419; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
5.702 |
Times cited |
157 |
Open Access |
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Notes |
Fwo; Iap |
Approved |
Most recent IF: 5.702; 2011 IF: 4.603 |
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Call Number |
UA @ lucian @ c:irua:84651 |
Serial |
3709 |
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| Permanent link to this record |
