Although nanoscale twinning is an effective means to enhance yield strength and tensileductility in metals, nanotwinned metals generally fail well below their theoretical strengthlimit due to heterogeneous dislocation nucleation from boundaries or surface imperfections.Here we show that Au nanowires containing angstrom-scaled twins (0.7 nm in thickness)exhibit tensile strengths up to 3.12 GPa, near the ideal limit, with a remarkable ductile-tobrittletransition with decreasing twin size. This is opposite to the behaviour of metallicnanowires with lower-density twins reported thus far. Ultrahigh-density twins (twin thicknesso2.8nm) are shown to give rise to homogeneous dislocation nucleation and plasticshear localization, contrasting with the heterogeneous slip mechanism observed in singlecrystallineor low-density-twinned nanowires. The twin size dependent dislocation nucleationand deformation represent a new type of size effect distinct from the sample size effectsdescribed previously.
展开▼
