Formation of the internal structure of solids under severe load

Effect of stochastic processes on structure formation in nanocrystalline materials under severe plastic deformation

Based on the nonequilibrium evolution thermodynamics, the structure refinement of metals during severe plastic deformation is investigated. To describe the formation of stationary (limiting) submicrocrystalline or nanocrystalline structures, a two-defect approximation, including the grain boundaries and dislocations, is used. Introduction of the additive noise for the main parameters into the governing equations allowed us to describe the self-consistent behavior of structural defects during the stationary structure formation. Conditions of achieving the stationary state are investigated and possible scenarios of structure refinement modes are determined. Obtained grain boundary density distributions help to estimate the composition of grain structure in the bulk of metal sample quantitatively. The analysis of time evolution of the grain boundaries density shows the presence of correlated fluctuations. The autocorrelation function, describing the frequency characteristics of the structure refinement, is determined.

Nonequilibrium dynamics of a two-defect system under severe load

In the framework of a two-defect model, based on a variation of the Landau technique, the kinetics of structural defect generation in solids under severe external load is investigated. The approach is based on a special form of kinetic equation in terms of internal energy, which is applied here to the description of an important practical problem of fine-grained structure formation in metals under severe plastic deformation. It unifies strengthening curves over the entire range of deformation, including the Hall-Petch and linear strengthening sections.

Nonequilibrium evolution thermodynamics of vacancies

An alternative approach, nonequilibrium evolution thermodynamics, is compared with the classical Landau approach. A statistical justification of the approach is done with the help of a probability distribution function on an example of a solid with vacancies. Two kinds of kinetic equations are derived in terms of the internal energy and the modified free energy.