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Temur Dzigrashvili

Georgian Technical University, (RCSR)

77 Kostava St. Tbilisi, 0175, Georgia

Phone: (+995 32) 236 14 03

Mob: (+995) 599 27 38 04

E-mail: dzigra@gtu.ge

 

Research: Crystallography of Twinning; Advanced Materials

Academic Preparation:

Doctor of Physics (Ph.d), 1995, Georgian Technical University, Tbilisi Georgia. Dissertation: The Crystallographic Theory of Twinning and Computer Simulation.

Candidate of Sciences, 1977, GTU.Thesis: Structural Transformations During Ordering in Cu-Pd and Fe-Pd Alloys

Institution: GIXI ingenierie informatique, Paris, France. Software course.06.1981 - 07 1981; Certificate (Attestation de stage).

Institution: Institute of Improvement of Skill of Information Workers (Specialty: International Systems of Scientific Information), Moscow, Russia.09.1979-10 1979; Certificate.

Institution: Graduate student at the Institute of Physics of Metals and Materials Science, (CNII Ch.M.), Moscow, Russia.09.1971 - 06.1972.

Institution: State Courses of Foreign Languages (English) Tbilisi, 09 1974 - 07 1975; Certificate.

Institution: Georgian Technical University, Tbilisi 09 1967 - 07 1972; Diploma of Engineer Physicist.

Professional Appointments:

1996 (current): Professor of Physics at the Georgian Technical University. Research: structural phase transformations in solid state; crystallography and computer simulation of diffraction processes; Lecturer

1992-1996: Leading research fellow at the Republic Center for Structure Researches (RCSR), GTU.

1987-1992: Head of the Sector for Computer Simulation of Physical Processes at RCSR, GTU.

1982-1987: Senior research fellow at the Republic Center for Electron Microscopy, GTU.

1980-1982: Senior research fellow at the Radiochemical Laboratory of the GTU. 1974-1980: Junior research fellow at the Radiochemical Laboratory of the GTU. 1972-1974: Assistant at the Department of General Physics, GTU.

Temporary appointments:

Summer 1977: Sabbatical at the Institute of Physics and Materials Science (CNII Ch.M.), Moscow, Russia.

Sept.75-July 76: Visiting Scientist at the Institute of Physics of Metals, Kiev, Ukraine.

Publications: 99, in Russian and in English. (incl. 2 guide books for students on X-ray characterizations and electron diffraction; in Georgian).

Professional societies: Georgian Physical Society; Georgian Academy of Ecology; Member of British Computer Society; Incorporated in the World Directory of Crystallographers

Language skills: Georgian (native), Russian(fluent), English(very good), German (poor).

Research Interests:

Crystallography of twinning in crystals

Prof. Dzigrashvili has developed a method of calculation of twinning modes and the Analytical Theory of Crystallography of Twinning providing prediction of the twinning elements from a knowledge of twinning plane and metric tensor of the crystal lattice.

Prof. Dzigrashvilis current research involves investigation and proof of the regularity found by him for twinning shear plane in compound twins. The regularity is formulated in the form of certain transformation (mapping). As a result a new procedure for determining the twinning shear plane and shear direction, from a knowledge only of twinning plane and the metric tensor of the crystal lattice is proposed. The transformation equation describing a specific mapping (SM) is proposed, which transforms a set of arbitrary vectors into a set of coplanar vectors, situated in the plane of the twinning shear. Miller indices of the shear planes and the indices of corresponding shear directions defined by this method for twinned crystals coincide with the experimental data. The analytical treatment based on the general theory (GT) of deformation twinning is shown, in order to test the accuracy of the suggested mapping. Agreement between the two (SM, GT) approaches was found to be excellent.

Mapping (1) transforms any set of arbitrary, generally non-coplanar, vectors u into a set of coplanar vectors D u, situated in the plane of twinning shear P. Thus, knowing the couple of D u , one can easily find the covariant components of the normal to the plane P, i.e., the Miller indices of P, as a vector product of the contravariant components of any couple of vectors D u. Then, taking into consideration the geometry of twins, the intersection of P with the plane of twinning K1, gives the direction of the twinning shear .

D u = (I-R)t u                                      (1)

Here, I is an identity matrix; R = Ds k; D is a mirror reflection matrix for the given twinning plane, and s k is a matrix of mirror reflection in the plane normal to the kth principal axis of the crystal lattice, so that s x s y and s z, represent the reflections in the planes normal to the axes [100], [010] and [001] respectively. Superscript t denotes transposition of the matrix.

Thus, by direct calculations it was shown that substitutions for s k (s x, s y, s z), in the relation (1), result in the three sets of covariant (reciprocal space) components of the normals to the possible three alternatives of P, and at least one of the sets represents the Miller indices of the operative plane of shear.

For practical application of the developed approach one may simply follow a hypothesis that in compound twins the shear plane P corresponding to the plane of twinning K1 contains not only the normal m to K1, as it follows from the definition of the plane P, but also one of the conventional basis vectors n = [100], [010] or [001] of the lattice, as a consequence of the proposed approach.

Actually the following algorithm may be used for calculation of twinning shear direction:

  1. Calculate the indices of the normal (m) to the plane of twinning K1, using the well-known crystallographic formulae.
  2. Calculate the Miller indices of the possible planes P as a vector product p = m x n, for each n, and then,
  3. The possible directions of twinning shear are calculated, by definition, as a vector product 1 = p x m.

Generally, one of the three calculated values of 1 (with rational indices) coincides with the experimentally determined one, with the accuracy of sign. Sure, for cubic crystals all the three values are operative because of symmetry. Here are some calculated examples in the table below.

Twinning modes calculated using the formulae given in [21] (Microscopy and Analysis, 2008), and some supporting experimental data

Notes: ---- experimental data not available to the author
* morphological system
1) exact value, (1 0.06 0).
2) exact value, (1 -3.991 0)

The crystallographic data are taken from:
N.V. Klassen-Neklyudova: Mechanical Twinning of Crystals. Plenum Press, NY 1964. Kelly, A.; Groves. G.W.: Crystallography and Crystal Defects. Longman, London 1970. Christian, J.W.: The Theory of Transformations in Metals and Alloys. Pergamon Press, Oxford 2002.

www.webmineral.com
www.webelements.com

Prof. Dzigrashvili has developed

The program pack for computer simulation of electron diffraction patterns and stereographic projections for single, twinned and two-phase crystals of any system. (ELDIST)

Computer generated schemes include crystal lattice parameters, direction of incident beam (zone axis), reciprocal lattice vectors, indexed scheme of diffraction pattern in readable scale and the same scheme in scale of microscope's l L. The program pack generates stereographic projections of directions and gnomostereographic projections of planes.

Prof. Dzigrashvili's research efforts focus on the following directions of Materials Science:

Structure of small particles of Boron
Computer simulation of structure of small particles (classical approach based on 6-12 potential of interatomic interaction).
Structure of whisker crystals of Boron
Corrosion of Chromium
Structure of high-carbon steels and austempered ductile iron

Publications:

1. Method of Derivation of Twin Relation Matrices for the Analysis of Electron Diffraction Pattern from Crystals of any System. Kristallografia, (1975), v.20, N5, p.p.965- 968 (in Russian).

2. Diffuse Scattering of Electrons and lattice Instability in Cu-Pd Alloy. Izvestia Vuzov SSSR, Fizika, (1976), N1, p.p.149- 152 (in Russian).

3. Structural Changes During Ordering of Fe-50at%Pd alloy. Fizika Metallov i Metallovedenie, (1977), v.43, N6, p.p. 1316-1319 (in Russian).

4. Peculiarities of Physical Properties and Ordering in Cu-Pd Alloys. Fizika Metallov i Metallovedenie, (1978), v.45, N6, p.p.1200-1202 (in Russian).

5. Computer Simulation of Electron Diffraction Patterns from Twinned Crystals. Kristallografia, (1980), v.25, N5, p.p.1060-1061 (in Rusian).

6. Computer Simulation of Electron Diffraction Patterns and Stereographic Projections for the Analysis of Two-Phase Crystals. Kristallografia, (1984), v. 29, N6, p.p1190- 1190 (in Russian).

7. Charasteristics of Electron Diffraction on Cementit Lattice Proceedings of 5-th Conference on Applied Cristallography. Vol.1 Kozubnik, Poland. September 10-14. 1984. p.p. 244-248.

8. Electron-microscopy Investigation of the Structure of Amorphous Boron. American Institute of Physics. Sov. Phys. Solid State 27(5) 1985.

9. Determination of the Mean Inner Potential of Single-crystal Lattices of Boron-Containing Materials and Its Relation to the Work Function. Elsevier, Sequoia, “Journal of Less-Common Metals”. 117,(1986) p.p. 283-286.

10. Electron Microscope Investigation of the Processes of Crystallization of ZrO2 Amorphous Films Prepared in Super-High Vacuum. ZIRCONIA'88 Advanced in Zirconia Science and Technology 7th SIMCER-International Simposium on Ceramics, ZIRCONIA’88 December (Edited by S. MERIANI University of Trieste). Bologna (Italy) December 14-16 1988 p.131-135 ELSEVIER, LONDON, NEW YORK.

11. Crystallography of Twinning of Batch Martensite and Internal Tension. Fizika Metallov I Metallovedenie, (1989), v.67, N3, p.p.518-524.

12. Peculiarities of internal Friction in Boron Carbide. AMERICAN INSTITUTE OF PHYSICS CONFERENCE PROCEEDINGS 231. Boron-Rich Solids ALBUQUERQUE, NM 1990, pp. 594-601 New York.

13. Physical properties and Structure of Ferroelectric-Feroelastic DMAAS Crystals. Proceedings of the International Symposium “Structure and Properties of Crystals. Moscow, 1991 July. Butll. Soc. Cat. Cien. Vol. C III, Num.1, 1992, Spain.

14. The crystallographic calculation of the elements of mechanical twinning in crystals. Zeitschrift fur Kristallographie (1995), 210, pp. 167-172. R.Oldenburg Verlag, Munchen.

15. The Analytical Theory of The Crystallography of Mechanical Twinning Ferroelectrics, Vol.175 pp.1-11(1996) U.S.A.

16. Electron Microscopic Study of The First Stages of Martensite Decomposition in Carbon Steel. Georgian Engineering News (1999), N1, p.p.5-15.

17. New High-Strength Deformable cast iron For Producing Wares by Pressing, Forging and Casting. Georgian Engineering News, (2000), N3, p.p.39-44.

18. Structural Mechanisms of Relaxation of Stresses During Shear-Like Transformation in High-Carbon Austenite. Proceedings of the International Metallurgy and materials Congress, Istanbul, Turkey, 24-28 May, 2000, p.p. 1975-1982.

19. Some Physical Properties of Compacted Specimens of Highly Dispersed Boron Carbide and Suboxide. Elsevier. Journal of Solid State Chemistry 177 (2004), p.p.596-599.

20. Interpretation of Electron Diffraction Patterns of Two-Phase and Twinned Crystals. Inteleqti Publishing House, Tbilisi, Georgia, (2005) 197p.(In Russian)

21. Computer Simulation of Electron Diffraction Patterns and Stereographic Projections. John Wiley & Sons LTD, Chichester, UK. Microcopy and Analysis, January (2008) p.p. 5-7.

22. The Analysis of Microcrack Plastic Zone Formed in the Films After LCF Tests of Austenitic Steel Used in NPP I. Trans tech Publications, Switzerland. Key Engineering Materials Vols. 417-418 (2010) p.p.109-112.

23.SEM Study of High-Chromium Martensitic Steel LCF Fracture. TransTech Publications, Switzerland. Key Engineering Materials Vol. 465 (2011), p.p. 298-301.

24.Study of Fracture Mechanisms at Cyclic Fatigue of Steels Used in Nuclear Reactors I. Steel Research International. V. 83, #3, 2012, p.p. 213-217.