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Investigation of the Dynamics of Defect Accumulation During Hydrogen Charge of Titanium

: Chernov, I.; Cherdantzev, Y.; Lider, A.; Garanin, G.; Surkov, A.S.; Nikitenkov, N.N.; Kröning, M.; Baumbach, H.

Mesomechanics: Foundations and Applications. International Workshop. Program and abstracts
Tomsk, 2001
International Workshop Mesomechanics <2001, Tomsk>
Fraunhofer IZFP ()
hydrogen charge; Titan

The hydrogen influence on the dynamics of defect formation in VTI-0 titanium was studied. Studying surface states of titanium used as cathodes at an electrolytic hydrogen charge from LiOH+H2O solution was performed by optical and raster electronic microscopes. The method of positron annihilation was used for studying concentration and types of defects in a bulk of metal. After a mechanical and electrochemical polish, samples of the 50x5x1 mm dimensions were explosed by vacuum annealing during 120 min at a temperature of 700°C followed by slow cooling. The electrolytic charge by hydrogen in a LiOH+H2O solution was performed at a current density 0,5-1 A/cm2 (platinum was used as the anode). The enriching of titanium bulk by hydrogen (for sample by 1 000 jm depth) up to maximum concentration is achieved for 4 hours under these conditions, as shown. Optical and raster electron microscopy has revealed a considerable amount of defects on the sample surface which appeared after enrichment with hydrogen. Already after 2 or 3 minutes of an electrolysis at a current density 1 A/cm2 on a metal surface there are dotted formations up to 1 jm in diameter. It is connected with the nonuniform evolving of the hydrogen phase of titanium, which grows from the surface to the depth of metal. A metal surface is coated fully with similar formations after 20-munites enriching. Craters (up to 10 jm in diameter) and cracks are found on a sample's after 120 minutes of a hydrogen enriching. The study of titanium bulk defects was performed by the positrons annihilation method. The results of the measurement of a positron life-time have shown that at about 150 microns depth, the fundamental contribution (up to 90%) is determined by single vacancies and dislocation. The greatest contribution in a long-lived component at spectrums decomposing of gamma - quantum's at a positron annihilation, defining the amount of largesized defects, brings a near-surface range of about 20 microns.