ELFT HÍRADÓ

[Zsolt Kovacs <kovacszs AT metal.elte.hu>]

                         MEGHIVO

             az ELTE TTK Anyagfizikai Tanszek
                     szeminariumara



                   Prof. Igor Alexandrov
     (Ufa State Aviation Technical University, Russia)

          Experimental study and computer modeling
               of severe plastic deformation



Helye: ELTE Fizikai Intezet, Anyagfizikai Tanszek
       1117 Budapest, Pazmany Peter setany 1/A, 4.emelet 4.52. terem

Ideje: 2006. szeptember 26. kedd, 8.30.

Minden erdeklodot szivesen latunk.
A 2006/2007. tanev I. felevi programja megtalalhato a kovetkezo cimen:
http://metal.elte.hu


                                     Kovacs Zsolt


Az eloadas rovid kivinata:

EXPERIMENTAL STUDY AND COMPUTER MODELING OF SEVERE PLASTIC
DEFORMATION

Igor Alexandrov

High pressure torsion (HPT) is one of most wide-spread
schemes for severe plastic deformation. This scheme is
often applied for analysis of scientific aspects,
connected with formation of bulk ultrafine-grained 
(UFG) and nanostructured states. At the same time the
investigation of the HPT process is a topical issue.
This is connected with its multiple-factor character.
In this work the results of experimental investigations
and computer modeling of processes, accompanying HPT of
pure copper are presented.
Analysis of the material flow features was made in
frames of the developed analytical model. The process
of the preferred orientations formation was studied in
frames of the viscous-plastic self-consistent model.
The interrelation between the components of the
stress-strain state and the features of structure- and
texture- formation in bulk billets, subjected to HPT,
was revealed.

The upgraded Estrin-Tóth dislocation model has been
suggested to describe deformation behavior of materials,
subjected to severe plastic deformation (SPD), which in
its turn is realized under high imposed pressure of
several GPa. The model was applied to study high pressure
torsion of Cu samples. The dislocation density evolution
has been studied in the two phases: in the fragment/cell
block boundaries and interiors. The evolution of
concentration of vacancies, obtained during the
deformation, and annihilation of dislocations during
their non-conservative motion, generation of dislocations
during multiple cross slip have been considered.
Accounting of hydrostatic pressure was made in an explicit
form on the basis of the presumption about limitation of
the lattice diffusion, controlled by pressure. As a result
the causes of achieving high values of flow stress, yield
stress, dislocation density, vacancy concentration have
been explained.