It is well known that the twinning an important mode of plastic deformation in nanocrystalline materials. As a result, it expected twin can interact with different grain boundaries (GBs) during deformation. Understanding these twin–GB interactions crucial for our understanding mechanical behavior In this work, interaction ?11 symmetric and asymmetric tilt GBs has been investigated BCC Fe using ...

Scanning electron microscopy transmission Kikuchi diffraction is able to identify twins in nanocrystalline material, regardless of their crystallographic orientation. In this study, it was employed to characterize deformation twins in Cu/10 wt % Zn processed by high-pressure torsion. It was found that in 83% of grains containing twins, at least one twin intersects with a triple junction. This s...

Although nanoscale twinning is an effective means to enhance yield strength and tensile ductility in metals, nanotwinned metals generally fail well below their theoretical strength limit 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 G...

In situ atomic-scale bending tests of twin-structured Ni nanowires were realised using a homemade deformation device. The results showed that the plastic mechanism in depended on stage. At early stages deformation, plasticity was controlled by dislocations interacting with twin boundaries or parallel to them. With increasing strain, both dislocation and face-centred cubic–body-centred tetragona...

We have revealed the fundamental embryonic structure of deformation twins using in situ mechanical testing of magnesium single crystals in a transmission electron microscope. This structure consists of an array of twin-related laths on the scale of several nanometers. A computational model demonstrates that this structure should be a generic feature at the incipient stage of deformation twinnin...

This letter presents a study of the atomic mechanism of the initiation of motion of a static twin plane under applied mechanical load in a model shape-memory material. By tracking the deformation under load and using linear stability analysis, we find that the eigenvalues of the Hessian matrix provide an indicator of the initiation of motion of the twin plane. The initiation of motion is signal...

By employing the in situ transmission electron microscopy (TEM) technique, tensile deformation behaviors of a silver nanowire (NW) with a single twin structure were studied. Our observations revealed that the initial stage of plastic deformation was dominated by surface-mediated partial dislocation activities. Strikingly, the void formation and growth were shown to govern the later stage of pla...

The elementary mechanisms controlling the interactions between lattice gliding dislocations and twin boundaries were carefully analyzed using conventional and advanced transmission electron microscopy techniques in both bulk coarsegrained Fe-Mn-C TWIP steels with deformation twins and nanocrystalline Palladium thin films with nanoscale growth twins. The results reveal that the individual disloc...

Deformation twinning at the tip of a straight crack or notch is analyzed using a phase-field method that seeks equilibrium twin morphologies via direct minimization of a free energy functional. For isotropic solids, the tendency to twin under mode I or mode II loading is found to depend weakly on Poisson’s ratio and elastic nonlinearity and strongly on surface energy and twinning shear (i.e. ei...

We employ classical molecular dynamics to calculate elastic properties and to model the nucleation and propagation of deformation twins in calcite, both as a pure crystal and with magnesium and aspartate inclusions. The twinning is induced by applying uniaxial strain to the crystal and relaxing all stress components except the uniaxial component. A detailed analysis of the atomistic processes r...