Papers by Author: Danil V. Vaganov

Abstract: Grain boundary (GB) diffusion of Ag in Cu-based alloys with Fe (0, 0.14, 0.29, 0.43, 0.55 and 0.99 at. % Fe) was investigated. The experiments were performed at 600, 650 and 700 °C, which corresponded to B-regime. It was proved by the presence of diffusion wedges. The triple product of silver GB diffusion was obtained by measuring of angle at the top of isoconcentration profiles which was detected by electrochemical etching. It was shown that iron decreased the triple product at higher temperatures and didnt affect significantly at lower temperatures. SEM investigation showed the presence of small (10-100 nm) precipitates on the copper grain boundaries. Analysis of particles composition by Auger electron spectroscopy indicated higher concentration of iron comparing with the alloy composition.

Abstract: The liquid bismuth penetration from solid bismuth telluride (Bi2Te3) into grain boundaries of copper and copper-based solid solutions was studied. The experiments were performed at 570 oC in hydrogen atmosphere. The copper specimens were annealed from 10 to 90 minutes. Solid Bi2Te3 didn’t contact with copper specimens during experiments, so copper was covered by the decay products of Bi2Te3 through the gas phase. Liquid Bi penetration leads to grain boundary embrittlement of copper. We assumed that the depth of penetration is equal to the length of cracks which are formed after sample bending. It was shown that there is only bismuth at the grain boundaries while on the surface tellurium also exists. Bismuth concentration in the grain boundaries measured by Auger spectroscopy was about 10-20 at. % and the width of penetration channel was less then 10 nm. Bismuth covered the grain boundaries uniformly. Time dependence of the penetration depth was approximately parabolic. In the present work the effect of impurities (silver, iron) on grain boundary liquid bismuth penetration was studied also. It was shown that silver accelerates the penetration in contrast to iron. The probable reasons were discussed.

Abstract: Degradation of the mechanical properties of copper and copper based alloys after the treatment with telluride bismuth (Bi2Te3) at 570oC has been studied in the present work. The experiments were performed in a H2 deoxidizing atmosphere. The kinetics of embrittlement of pure copper has been shown to be parabolic. Bi2Te3 was in the solid state and was not in direct contact with the copper specimens during the experiments, i.e. the plating was performed through the gas phase. The brittle fracture along the GB was observed after 3 point bending test. The surface of fracture was investigated with the use AES. It was shown that intergranular penetrations of liquid bismuth and bismuth from Bi2Te3 have different mechanisms.

Abstract: Grain boundary surface tension and surface tension of free surface for pure copper and copper-tin alloys are measured. On the base of these data isothermes of grain boundary tension, free surface tension and isothermes of adsorption are constructed in assumption of a dilute solution.

Abstract: Indirect method is used for determination of copper self-diffusion coefficient on the base of high-temperature creep data. These data are obtained by the use of the new measuring device and assuming that Nabarro-Herring mechanism acts.