期刊
SCIENCE
卷 323, 期 5914, 页码 607-610出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1167641
关键词
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资金
- National Natural Science Foundation of China [50431010, 50621091, 50725103, 50890171]
- Ministry of Science and Technology of China [2005CB623604]
- Danish National Research Foundation
The strength of polycrystalline materials increases with decreasing grain size. Below a critical size, smaller grains might lead to softening, as suggested by atomistic simulations. The strongest size should arise at a transition in deformation mechanism from lattice dislocation activities to grain boundary- related processes. We investigated the maximum strength of nanotwinned copper samples with different twin thicknesses. We found that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced strain hardening and tensile ductility. The strongest twin thickness originates from a transition in the yielding mechanism from the slip transfer across twin boundaries to the activity of preexisting easy dislocation sources.
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