In this paper, the microstructural and hardness evolutions of an Mg-5.91Gd-3.29Y-0.54Zr (wt%) alloy during high-pressure torsion (HPT) were investigated. Deformation twinning played a crucial role in HPT-induced grain subdivision process. 1/8-revolution disk, 101¯1 101¯2 twins with different twin variants, 101¯1−101¯2 secondary twin-twin interactions activated. Primary prevailed at very central...

Recent studies have shown that strength values similar to those observed in nanocrystalline metals can be obtained without a severe deterioration in ductility. This is achieved by introducing controlled, nanoscale, growth twins within ultrafine-grained metals. In this work, we present a continuum description of the effective response of nanotwinned ultrafine crystals. The model is based on a fi...

We have investigated the rate sensitivity of flow stress and the extent of strengthening in polycrystalline copper containing different volume fractions of nano-sized twins, but having the same average grain size. The specimens were produced by pulsed electrodeposition, wherein the concentration of twins was varied systematically by varying the processing parameters. Depth-sensing instrumented ...

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 ...

This article systematically overviews the grain size effect on deformation twinning and detwinning in face-centered cubic (fcc) metals. With decreasing grain size, coarse-grained fcc metals become more difficult to deform by twinning, whereas nanocrystalline (nc) fcc metals first become easier to deform by twinning and then become more difficult, exhibiting an optimum grain size for twinning. T...

The role of 5-fold twin boundary on the structural and mechanical properties of fcc Fe nanowire under tension is explored by classical molecular dynamics. Twin-stabilized fcc nanowire with various diameters (6-24 nm) are examined by tension tests at several temperatures ranging from 0.01 to 1100 K. Significant increase in the Young's modulus of the smaller nanowires is revealed to originate fro...

β-type Ti-29Nb-13Ta-4.6Zr alloy is a promising novel material for biomedical applications. We have proposed a 'single crystalline β-Ti implant' as new hard tissue replacements for suppressing the stress shielding by achieving a drastic reduction in the Young's modulus. To develop this, the orientation dependence of the plastic deformation behavior of the Ti-29Nb-13Ta-4.6Zr single crystal was fi...

The strain-rate sensitivity of ultrafine-crystalline Cu with different concentrations of nanoscale growth twins is investigated using tensile strain rate jump tests. Higher twin density leads to enhanced rate sensitivity, which decreases mildly with increasing strain rate and strain. Mechanisms underlying these effects are explored through post-deformation transmission electron microscopy. 2006...

To investigate the role of preexisting twin boundaries in magnesium alloys during the deformation process, a large number of {10-12} tensile twins were introduced by a radial compression at room temperature before hot compressive tests with both low and high strain rates. Unlike the stable twins in Cu-based alloys with low stacking fault energies, {10-12} twins in Mg alloy are extremely unstabl...