Universal Mechanism of Viscoplastic Deformation of Metallic Materials Far from Thermodynamics Equilibrium

Abstract

The article gives results of structure formation in metallic materials after different types of deformation: tungsten after rolling, nickel after thermal cycling and nickel single crystal after rolling, aluminum single crystal after cyclic tension and aluminum alloys (D16, 2024-T3) after impulsive load. We used optical and electron microscopy methods for investigation of deformation structure formation and molecular dynamics method for computer modeling of the processes of plastic deformation (LAMMPS software). The following quantitative parameters were calculated during the simulation: energy of pair interaction, temperature, total cumulative pressure, stress tensor and pressure tensor. The study shows that the plastic flow of metallic materials with any initial structure at certain loading stage can be carried out by homogeneous mass transfer through channels with a liquid-like structure, from which follows that the dislocation mechanism of plastic deformation of crystals has a limited field of application. The main role has a synergistic structure formation in the conditions of distance from thermodynamic equilibrium. The relaxation processes proceed intensively after and during the process of destruction. The results of modeling have shown the possibility of forming channels of hydrodynamic flow without the participation of defects in the initial material.

Appendix

Q :

is amount of material released to the surface through the surface cross section of the channel during the time t;

e :

deformation (e ~ ϴ);

λ :

is the initial length of the channel;

$\sigma \left( t \right) = \sigma_{zz}$ :

is the component of the tensile stress, which is applied to the sample (all other components are equal to zero);

P :

is the pressure of the “liquid”;

γ :

is the kinematic viscosity;

ρ :

is the density of the “liquid”;

η :

is the coefficient of dynamic viscosity of the “liquid”;

D :

is the integration constant [D = D(t)];

l :

is the length of the channel;

k, k₁, k₂:

that do not depend on any variable;

b, b′:

are constants;

q :

is the cyclic load frequency;

y :

is the cyclic loading phase;

r ₀ :

is the radius of the section of the hydrodynamic channel;

r :

is the coordinate along the radius of the section of the hydrodynamic channel;

v _r :

is the velocity of movement of the “fluid” within the channel along the coordinate;

φ :

is the rotation angle in the XOY plane;

v _φ :

is the “fluid velocity” along the coordinate φ;

v _z :

is the “fluid velocity” along the axis OZ