Dislocation nucleation facilitated by atomic segregation

Abstract

Surface segregation—the enrichment of one element at the surface, relative to the bulk—is ubiquitous to multi-component materials. Using the example of a Cu–Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

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Figure 1: Au surface segregation in the Cu(Au) solid solution.
Figure 2: In situ TEM observation of the birth of misfit dislocations out of a coherent Cu3Au/Cu(Au) interface.
Figure 3: HRTEM characterization of the misfit dislocations and in situ TEM observations of the dislocation migration by glide and climb (at 350 °C and 1 × 10−3 torr of H2 gas flow).
Figure 4: Modelling of the near-surface dislocation behaviour.

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Acknowledgements

This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0001135. The authors thank H. Chi and S. House for their help in specimen preparation and testing. This research used resources of the Center for Functional Nanomaterials, which is a US DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. This work used the computational resources from the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number OCI-1053575. C.Y. and L.Q. acknowledge the computational resources and services provided by Advanced Research Computing at the University of Michigan, Ann Arbor.

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G.Z. and L.Z. conceived the idea and designed the experiments. D.Z., L.Z., Q.Y., D.S. and E.A.S. performed the experiments. C.Y., Y.L., Z.L. and J.L. performed the DFT and MD simulations under the supervision of L.Q. and G.W. L.Z., G.Z., L.Q., Y.L. and C.Y. analysed the data. L.Z., G.Z., L.Q. and J.M.K.W. wrote the manuscript. G.Z. supervised the whole project. All the authors discussed the results and implications and commented on the manuscript.

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Correspondence to Guangwen Zhou.

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The authors declare no competing financial interests.

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Zou, L., Yang, C., Lei, Y. et al. Dislocation nucleation facilitated by atomic segregation. Nature Mater 17, 56–63 (2018). https://doi.org/10.1038/nmat5034

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