We posited that the grain size dependence of tensile necking stress, as determined by Considère criterion for plastic instability, is a more meaningful characteristic Hall–Petch (H–P) effect than yield stress or 0.2% proof stress. An inverse square-root on was derived from dislocation dynamics-based constitutive model. In this model, enters indirectly via evolution density. Model predictions we...

In recent years it has become possible to study the properties of nanocrystalline metals through atomic-scale simulations of systems with realistic grain sizes. A brief overview of the main results is given, such as the observation of a reverse Hall-Petch effect — a softening of the metal when the grain size is reduced. The limitations of computer simulations are discussed, with a particular fo...

2014 The use of the Hall-Petch relation in texture simulations with the Taylor-Bishop-Hill model is proposed as a mean to take into account grain shape effect. The results are compared with those obtained with the usual and relaxed constraint Taylor model for a simple texture and the consequences for the anisotropy coefficient are investigated. J. Physique Lett. 46 (1985) L-1109 L-1113 1 er DEC...

The partial dislocation model for the deformation mechanism of nanocrystalline materials is extended to consider the influence of non-uniform dislocation extension. The non-uniform partial dislocation extension model is more consistent with experimental data than the original partial dislocation model. Additionally, the flow stress obtained from the non-uniform extension model is compared with ...

The fracture of polycrystalline graphene is explored by performing molecular dynamics simulations with realistic finite-grain-size models, emphasizing the role of grain boundary ends and junctions. The simulations reveal a ~50% or more strength reduction due to the presence of the network of boundaries between polygonal grains, with cracks preferentially starting at the junctions. With a larger...

Strengthening by grain refinement via the Hall–Petch mechanism and softening nanograin formation inverse have been subject of argument for decades, particularly ultrafine-grained materials. In this study, relationship is examined magnesium, aluminum, copper, iron produced severe plastic deformation in literature. Magnesium, their alloys follow with a low slope, but an up-break appears when size...

Nanocrystalline materials show a higher strain-rate sensitivity in contrast to the conventional coarse-grained materials and a different grain size dependency. To explain these phenomenon, a finite element model is constructed that considers both grain interior and grain boundary deformation of nanocrystalline materials. The model consist of several crystalline cores with different orientations...