The viscoplastic deformation of polycrystals under uniaxial loading is investigated to determine the relationship between hot spots in stress and their location in relation to the microstructure. A 3D full-field formulation based on fast Fourier transforms for the prediction of the viscoplastic deformation of poly-crystals is used with rate-sensitive crystal plasticity. Two measured polycrystal...

The relationship between tensile elongation and acoustic emission (AE) detected during compressive deformation of 81-Li and Al-Li-Zr alloys has been investigated for a range of microstructure. For comparison, AE measurements have been carried out for A1-Cu and commercial 7050 alloys. In the polycrystalline binary A1-Li alloys, the most pronounced AE was detected in the underaged condition durin...

In their as-fabricated state, nanocrystalline (nc) materials, consisting of individual grains or crystallites with diameters less than 100 nm, are systems that exist far from equilibrium. The large volume fraction of grain boundaries (GB) present in these materials contains considerable excess free energy, which provides a large driving force for grain growth. Grain growth in nc materials has b...

The exceptional properties of nanocrystalline materials lend themselves to a wide range of structural and functional applications. There is recent evidence to suggest that grain boundary impurities may have a dramatic effect on the stability, strength and ductility of nanocrystalline metals and alloys. In this study, transmission electron microscopy and atom probe tomography were used to charac...

The statistical-thermodynamic dislocation theory developed in previous papers is used here in an analysis of yielding transitions and grain-size effects in polycrystalline solids. Calculations are based on the 1995 experimental results of Meyers, Andrade, and Chokshi [Metall. Mater. Trans. A 26, 2881 (1995)MMTAEB1073-562310.1007/BF02669646] for polycrystalline copper under strain-hardening cond...

Despite observations of massive methane release and geohazards associated with gas hydrate instability in nature, as well as ductile flow accompanying hydrate dissociation in artificial polycrystalline methane hydrates in the laboratory, the destabilising mechanisms of gas hydrates under deformation and their grain-boundary structures have not yet been elucidated at the molecular level. Here we...

We study grain boundaries between striped phases in the prototypical Swift-Hohenberg equation. We propose an analytical and numerical far-field-core decomposition that allows us to study existence and bifurcations of grain boundaries analytically and numerically using continuation techniques. This decomposition overcomes problems with computing grain boundaries in a large doubly periodic box wi...

The grain size refinement of AISI 422 martensitic stainless steel in the temperature range of 950-1150 ºC was investigated by hot deformation tests. The deformed specimens were held at deformation temperature with delay times of 5 to 300s after achieving a strain of 0.3. The austenite grains exhibit a considerable growth at temperature higher than 1050˚C, while the grain coarsening is negligibl...

A finite element analysis of the large deformation of three-dimensional polycrystals is presented using pixel-based finite elements as well as finite elements conforming with grain boundaries. The macroscopic response is obtained through volumeaveraging laws. A constitutive framework for elasto-viscoplastic response of single crystals is utilized along with a fully-implicit Lagrangian finite el...