Thermodynamics and kinetics of solids fragmentation at severe plastic deformation

TL;DR

This paper develops a thermodynamic model to describe defect formation and grain size evolution during severe plastic deformation, revealing how elastic strains influence limiting structures and defect densities.

Contribution

It extends nonequilibrium thermodynamics to model defect dynamics and structure formation under severe plastic deformation, including defect interactions and kinetic processes.

Findings

Grain sizes decrease with increasing elastic strains.

Conditions for formation of different limiting structures are identified.

Dislocation and grain boundary densities evolve in tandem.

Abstract

The approach of nonequilibrium evolution thermodynamics earlier offered is developed. It helps to describe the processes of defect formation within the adiabatic approximation. The basic equations system depends on the initial defects distribution (dislocations and grain boundaries). The phase diagram is determined with the domains of the realization of different limiting structure types. The interaction effect of several defect types on the formation of a limiting structure is investigated in terms of the internal energy. The conditions of the formation of two limiting structures are found. The kinetics of the steady-state values establishment of the defects density is investigated within the scope of the adiabatic approximation. The dislocations density change follows the evolution of the grain boundaries density in this approach. It is shown that grain sizes, in limiting structures, decrease with an increase of the elastic strains.