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dc.contributor.authorCheng, Zhaoen_US
dc.contributor.authorBu, Linfengen_US
dc.contributor.authorZhang, Yinen_US
dc.contributor.authorWu, HengAnen_US
dc.contributor.authorZhu, Tingen_US
dc.contributor.authorGao, Huajianen_US
dc.contributor.authorLu, Leien_US
dc.identifier.citationCheng, Z., Bu, L., Zhang, Y., Wu, H., Zhu, T., Gao, H. & Lu, L. (2022). Unraveling the origin of extra strengthening in gradient nanotwinned metals. Proceedings of the National Academy of Sciences of the United States of America, 119(3).
dc.description.abstractMaterials containing heterogeneous nanostructures hold great promise for achieving superior mechanical properties. However, the strengthening effect due to plastically inhomogeneous deformation in heterogeneous nanostructures has not been clearly understood. Here, we investigate a prototypical heterogeneous nanostructured material of gradient nanotwinned (GNT) Cu to unravel the origin of its extra strength arising from gradient nanotwin structures relative to uniform nanotwin counterparts. We measure the back and effective stresses of GNT Cu with different nanotwin thickness gradients and compare them with those of homogeneous nanotwinned Cu with different uniform nanotwin thicknesses. We find that the extra strength of GNT Cu is caused predominantly by the extra back stress resulting from nanotwin thickness gradient, while the effective stress is almost independent of the gradient structures. The combined experiment and strain gradient plasticity modeling show that an increasing structural gradient in GNT Cu produces an increasing plastic strain gradient, thereby raising the extra back stress. The plastic strain gradient is accommodated by the accumulation of geometrically necessary dislocations inside an unusual type of heterogeneous dislocation structure in the form of bundles of concentrated dislocations. Such a heterogeneous dislocation structure produces microscale internal stresses leading to the extra back stress in GNT Cu. Altogether, this work establishes a fundamental connection between the gradient structure and extra strength in GNT Cu through the mechanistic linkages of plastic strain gradient, heterogeneous dislocation structure, microscale internal stress, and extra back stress. Broadly, this work exemplifies a general approach to unraveling the strengthening mechanisms in heterogeneous nanostructured materials.en_US
dc.description.sponsorshipAgency for Science, Technology and Research (A*STAR)en_US
dc.description.sponsorshipNanyang Technological Universityen_US
dc.relation.ispartofProceedings of the National Academy of Sciences of the United States of Americaen_US
dc.rights© The Authors. This article is distributed under Creative Commons Attribution-NonCommercialNoDerivatives License 4.0 (CC BY-NC-ND).en_US
dc.subjectEngineering::Mechanical engineeringen_US
dc.titleUnraveling the origin of extra strengthening in gradient nanotwinned metalsen_US
dc.typeJournal Articleen
dc.contributor.schoolSchool of Mechanical and Aerospace Engineeringen_US
dc.contributor.organizationInstitute of High Performance Computing, Agency for Science, (A*STAR)en_US
dc.description.versionPublished versionen_US
dc.subject.keywordsGradient Nanotwinned Metalen_US
dc.subject.keywordsExtra Strengtheningen_US
dc.description.acknowledgementL.L. acknowledges support from the National Natural Science Foundation of China (Grants 51931010 and 92163202), the Key Research Program of Frontier Science and International Partnership Program (Grant GJHZ2029), the Chinese Academy of Sciences, and the LiaoNing Revitalization Talents Program (Grant XLYC1802026). Z.C. acknowledges support from the National Natural Science Foundation of China (Grant 52001312) and the China Postdoctoral Science Foundation (Grants BX20190336 and 2019M661150). H.G. acknowledges a research startup grant (002479-00001) from Nanyang Technological University and the Agency for Science, Technology and Research (A*STAR) in Singapore.en_US
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