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...

The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here betwee...

Graphene and carbon nanotubes have a Steiner minimum tree structure, which endows them with extremely good mechanical electronic properties. A modified Hall-Petch effect is proposed to reveal the enhanced strength of SiC/graphene composites, fractal approach its analysis given. Fractal laws for electrical conductivity graphene, graphene/SiC composites are suggested using two-scale theory. The s...

Abstract The temperature evolution of the Hall–Petch parameters for basal slip and twinning systems has been evaluated AZ31 alloy, using synchrotron radiation diffraction during compression tests from room to 473 K. alloy was processed following two processing routes, casting powder metallurgy, obtain different grain sizes with a similar strong fiber texture. Although macroscopic plasticity is ...

A theoretical model is suggested which describes the yield stress dependence on grain size in fine-grained materials, based upon competition between conventional dislocation slip, grain boundary diffusional creep (Coble creep) and triple junction diffusional creep. In the framework of the model, the contribution of diffusional creep mechanisms to plastic deformation increases with reduction of ...

High-pressure torsion (HPT) is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of ~50 nm after a rotation for 180◦. The microstructure evolution is associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinement. Deform...

We examine the role of atomistic simulations in multiscale modeling of mechanical behavior of stressed solids. Theoretical strength is defined through modes of structural instability which, in the long wavelength limit, are specified by criteria involving elastic stiffness coefficients and the applied stress; more generally, strength can be characterized by the onset of soft vibrational modes i...

Aluminum alloys with nanocrystalline (NC) and ultrafine grain (UFG) size are of interest because of their strengths that are typically 30 pct greater than conventionally processed alloys of the same composition. In this study, UFG AA 5083 plate was prepared by quasi-isostatic (QI) forging of cryomilled powder, and the microstructure and mechanical behavior was investigated and compared with the...

Effects of solutes on saturation grain size and mechanical properties are investigated for the Cantor alloy Ni-enriched variations ((CrMnFeCo)xNi1-x) with x=0.8, 0.4, 0.08 0. Indentation coarse-grained severely deformed states shows increasing hardness alloying content due to higher solid solution strengthening Hall-Petch contributions. Nanoindentation strain rate jump tests reveal similar sens...