Grain Boundaries and Mechanical Properties of Ultrafine-Grained Metals

Abstract

The concept of grain boundary (GB) engineering of ultrafine-grained (UFG) metals and alloys is developed for enhancement of their properties by tailoring different GBs (low-angle and highangle ones, special and random, or equilibrium and nonequilibrium) and formation of GB segregations and precipitations by severe plastic deformation (SPD) processing. In this article, using this approach and varying regimes and routes of SPD processing, we show for several light alloys (Al and Ti) the ability to produce UFG materials with different GBs, and this can have a dramatic effect on the mechanical behavior of the processed materials. This article demonstrates also several new examples of attaining superior strength and ductility as well as enhanced superplasticity at low temperatures and high strain rates in various UFG metals and alloys.

Microstructure and Mechanical Properties of Oxide-Dispersion Strengthened Al6063 Alloy with Ultra-Fine Grain Structure

“…During the last 10 years, UFG materials have attracted significant attention as a result of their enhanced mechanical strength at room temperature. [20] Improvement in mechanical properties of coarse-grained (CG) materials through SPD processes (e.g., equal channel angular extrusion [ECAE], [21] accumulative roll bonding, [22] and high-pressure torsion [23] ) has been commonly stated. High-strength bulk nanostructured and UFG materials also are prepared through consolidation of mechanically alloyed powders.…”

Turning the nuclear energy density functional method into a proper effective field theory: reflections

“…For static ρ(x), Γ [ρ] is proportional to the conventional Hohenberg-Kohn energy functional, which by eq. (12) is extremized at the ground state density ρ gs (x) (note that thermodynamic arguments establish that it is a minimum [88]). 4 Consider the partition function in the zero-temperature limit of a Hamiltonian with time-independent source J(x) [89]:…”

Toward ab initio density functional theory for nuclei

“…(Time-dependent sources can be used for certain excited states.) It is profitable to think in terms of a thermodynamic formulation of DFT, which uses the effective action formalism [32] applied to composite operators to construct energy density functionals [123,124,125]. The basic plan is to consider the zero temperature limit of the partition function Z for the (finite) system of interest in the presence of external sources coupled to various quantities of interest (such as the fermion density).…”

“…For static ρ(x), Γ[ρ] is proportional to the conventional Hohenberg-Kohn energy functional, which by Eq. (145) is extremized at the ground state density ρ gs (x) (and thermodynamic arguments establish that it is a minimum [124]). 17 Consider the partition function in the zero-temperature limit of a Hamiltonian with time-independent source J(x) [120]:…”

“…2. The inversion method [129,124,130,131] yields a systematic Kohn-Sham DFT, based on an orderby-order expansion. For example, we can apply the EFT power counting for a dilute system.…”