... mechanisms based on the gradient of dislocation density and grain size, back stress fields of grain boundaries, dislocation density transmission across grain boundaries, and stress/strain gradient effects. There is a tradeoff between improved ductility or higher strength in polycrystalline metallic...

...Khaled J. Al-Fadhalah The effect of texture on grain boundary character distribution (GBCD) in thermomechanically processed oxygen-free high-conductivity copper has been investigated. Copper samples were cold rolled to a reduction in thickness of 50% and then annealed for 60 min in the range of 400...

...Hongsuk Lee; Vikas Tomar Silicon carbide (SiC) is an important ceramic material usually found in polycrystalline form with grain boundary thickness ranging from a few nanometers to a few hundred nanometers and grains with multiple orientations with sizes of the order of few micrometers. The present...

... in the finite element model where the grain boundary was taken as the primary path for oxygen diffusion. The model has been used to simulate natural diffusion of oxygen at temperatures between 650 ∘ C and 800 ∘ C , which are controlled by the parabolic oxidation rate and oxygen diffusivity. To study the effects...

... properties at a small scale by taking into account the effect of inhomogeneities such as grain boundaries, bimaterial interfaces, slip lines, and inclusions. In particular, the depletion potential of the cohesive interface is made consistent with the atomistic potential inside the bulk material...

...Douglas E. Spearot; David L. McDowell The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials. Atomistic simulations...

... to grain refinement, with the average grain size decreasing with temperature. Moreover, a steady state grain aspect ratio and inclination of the grain long axis with respect to the shear plane is observed. With increasing shear strain, the fraction of low angle grain boundaries goes over a maximum...

... imply the coalescence of subgrains of or close to this orientation, and therefore the disappearance of existing high angle boundaries ( ≥ 15 deg ) . It is believed that the preference of D1 over D2, or vice versa, could be related to phenomena other than glide-induced rotations, e.g., grain boundary...

... of the development of the spatial anisotropy of such networks with increasing deformation provide a basis for defining several measures of the local total strain. These quantities, called “grain strains” when the boundaries observed are grain boundaries, can serve as an experimental measure of the internal total...

...Eric Loomis; Pedro Peralta; Damian C. Swift Two methods have been used to simulate 2D elastic wave scattering in nickel aluminide ( NiAl ) bicrystals to study effects of grain boundaries and material anisotropy on elastic wave propagation. Scattering angles and amplitude ratios of the reflected...

... are appropriately investigated. It is demonstrated that the model can correctly describe the overall and local damaged behavior of polycrystals. micromechanics stress-strain relations fracture mechanics fatigue internal stresses tensile testing compressive testing elasticity grain boundaries slip...

... are developed near grain boundaries, and conversely smaller gradients at high temperatures (i.e., low Z values). The frequency of thermally activated grain boundary motion coupled with various levels of local orientation gradients lead to the operation of different mechanisms of DRX nucleation. At warm...

... by the uniaxial conditions expected at the notch tips. In addition, crack path tortuosity was more pronounced in grains with loading axes close to 〈111〉. Finally, the influence of changes on slip geometry as cracks moved across grain boundaries is also discussed. The lateral surfaces of the samples were...

...L. Capolungo; M. Cherkaoui; J. Qu A self-consistent scheme is used to describe the behavior of nanocrystalline F.C.C. materials. The material is approximated as a composite with two phases. The inclusion phase represents the grain cores while the matrix phase represents both grain boundaries...

... into the Tvegaard’s axis-symmetric model for the constrained grain boundary rupture analysis. Based on the physically realistic Murakami–Ohno creep law, it is shown that the cavity growth becomes unconstrained upon the stress reversal from compression to tension. This leads to the prediction that the material life...

..., representing an idealized high-angle grain boundary interface. The interface model is subjected to three different deformation paths: tension then shear, shear then tension, and combined proportional tension and shear. Analysis shows that path-history dependent material behavior is confined within a finite...

...Y. Liang; P. Sofronis Experimental evidence indicates that nickel-base alloys fail in the presence of hydrogen by ductile intergranular fracture. The degradation mechanism involves void nucleation at grain boundary carbides and grain boundary decohesion. In this study, a micromechanical model...

... melted zone during tensile testing. Combined nanoindentation with in-situ AFM imaging reveal that the hardness at the partially melted zone is distributed inhomogeneously on the microscopic scale. The hardness at the area adjacent to the grain boundary is lower than that at the center of grain...

... September 2001 15 March 2002 10 06 2002 plasticity indentation hardness slip plastic flow bending tensors elasticity torsion free energy grain boundaries dislocation loops boundary-value problems crack-edge stress field analysis dislocation interactions There has been...

... analyzer system. In the experiments the 0.1 mm thin foil specimens of pure nickel and copper were gradually loaded toward final failure and the evolution of grain boundaries and slip bands inside grains was observed and recorded digitally via microscope and CCD camera throughout the whole time history...