History-independent cyclic response of nanotwinned Cu
||Prof. LU Lei|
Institute of Metal Rwsearch, Chinese Academy of Sciences
||Exhibition Hall, Hefei National Laboratory Building|
Nearly 90% of service failures of metallic components and structures are caused by fatigue at cyclic stress amplitudes much lower than the tensile strength of the materials involved. A long-standing obstacle to developing better materials has been that metals typically suffer from large, accumulative, irreversible damages in microstructure during cyclic deformation, leading to history-dependent and unstable cyclic responses. In this study, through both experiments and atomistic simulations, we report a history-independent and stable fatigue response in a bulk polycrystalline Cu sample containing highly oriented nanoscale twins under sequences of stepwise increasing/decreasing plastic strain amplitudes. The results demonstrate that this unusual behavior is governed by a type of highly correlated necklace dislocations formed in the nanotwinned metal under cyclic loading. This unique fatigue mechanism is fundamentally distinct from traditional strain-localizing fatigue mechanisms associated with irreversible microstructural damage.
||Hefei National Laboratory for Physical Sciences at the Microscale|
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