Ting Zhu, Ju Li, Amit Samanta, Hyoung Gyu Kim and Subra Suresh

Nano-twinned copper exhibits an unusual combination of ultrahigh strength and high ductility, along with increased strain-rate sensitivity. We develop a mechanistic framework for predicting the rate sensitivity and elucidating the origin of ductility in terms of the interactions of dislocations with interfaces. Using atomistic reaction pathway calculations, we show that twin boundary (TB) mediated slip transfer reactions are the rate-controlling mechanisms of plastic flow. We attribute the relatively high ductility of nano-twinned copper to the hardenability of TBs as they gradually lose coherency during deformation. These results offer new avenues for tailoring material interfaces for optimized properties.

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