Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

TLDR

Nano‑twinned copper uniquely combines ultrahigh strength, high ductility, and increased strain‑rate sensitivity. The study develops a mechanistic framework to predict rate sensitivity and explain ductility by examining dislocation–interface interactions. Atomistic reaction‑pathway calculations reveal that slip transfer across twin boundaries controls plastic flow. The high ductility is attributed to twin‑boundary hardening as coherency is lost, indicating that interfacial engineering can optimize strength and ductility.

Abstract

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 slip transfer reactions mediated by twin boundary are the rate-controlling mechanisms of plastic flow. We attribute the relatively high ductility of nano-twinned copper to the hardening of twin boundaries as they gradually lose coherency during plastic deformation. These findings provide insights into the possible means of optimizing strength and ductility through interfacial engineering.