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In situ observation of dislocation nucleation and escape in a submicrometre aluminium single crystal


‘Smaller is stronger’ does not hold true only for nanocrystalline materials1 but also for single crystals2,3,4,5. It is argued that this effect is caused by geometrical constraints on the nucleation and motion of dislocations in submicrometre-sized crystals6,7. Here, we report the first in situ transmission electron microscopy tensile tests of a submicrometre aluminium single crystal that are capable of providing direct insight into source-controlled dislocation plasticity in a submicrometre crystal. Single-ended sources emit dislocations that escape the crystal before being able to multiply. As dislocation nucleation and loss rates are counterbalanced at about 0.2 events per second, the dislocation density remains statistically constant throughout the deformation at strain rates of about 10−4 s−1. However, a sudden increase in strain rate to 10−3 s−1 causes a noticeable surge in dislocation density as the nucleation rate outweighs the loss rate. This observation indicates that the deformation of submicrometre crystals is strain-rate sensitive.

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Figure 1: Submicrometre tensile testing sample of single crystal aluminium.
Figure 2: Dislocation loops formed during tensile loading.
Figure 3: Dislocation emission by the operation of single-ended spiral sources.
Figure 4: Typical escape process of a long dislocation with accompanying single cross-slip.
Figure 5: Dislocation density measured as a function of the axial strain.


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Part of this work was supported by the Austrian Academy of Sciences. S.H.O. gratefully acknowledges financial support by the Korea Basic Science Institute grant (N28078). Recurrent financial support from the Centre National de la Recherche Scientifique was used to complete the TEM experiments in the framework of the ESTEEM European program.

Author information




S.H.O. and M.L. carried out the TEM experiments. S.H.O. and D.K. prepared the tensile testing sample using FIB. S.H.O. analysed the data, interpreted and discussed the results and wrote the paper. M.L., D.K. and D.L. revised the paper. M.L. double-checked the data analysis and refined the strain-rate calculation. G.D. conceived and designed the experiments.

Corresponding authors

Correspondence to Sang Ho Oh or Daniel Kiener.

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Oh, S., Legros, M., Kiener, D. et al. In situ observation of dislocation nucleation and escape in a submicrometre aluminium single crystal. Nature Mater 8, 95–100 (2009).

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