Papers by Author: Nikolai Dolgopolov

Abstract: According to different experimental data the grain boundary diffusion the triple product (P) can change in opposite directions after alloying. In this paper the analysis of the effect of alloying for different systems is proposed. It was shown that in Al-based system (Cu diffusion in Al, Zn diffusion in Al) the P value increases with alloying while the solidus temperature according to the phase diagram decreases, in other systems no such tendency can be seen. Estimations based on the segregation factor value demonstrate that some structural effect must be proposed in addition to describe the experimental results.

Abstract: Effect of microalloying of Al by Ce on Cu grain boundary diffusion (GBD) in Al and other results of GBD study in metals with different purity were analyzed. It is shown that in dependence on the chemical composition of the matrix the triple product of GB diffusion can be higher or less than that for pure metals. The main concept used for description of the results is local ordering of the atoms (including atomic complex formation and appearance of «poisonous» places around atoms of the alloying element). The increasing of atom mobility at GB is discussed also in terms of solidus temperature changes.

Abstract: The diffusion of Cu in Al and Al based alloys was studied. It was shown the great scattering of triple product values, measured for different grain boundaries (GB) at the same samples. It was discussed in the terms of GB energy difference. It was also shown that GB triple product can be varied significantly by preliminary alloying of Al by 0.1% Cu. However, the alloying of Al by 0.5% Cu leads to disappearing of the effect of accelerated diffusion in GB in comparison with the bulk.

Abstract: The interaction of liquid metals with solid polycrystalline metal leads to the appearance of liquid grooves at grain boundaries. The shapes of these grooves may be of a very wide variety. In this paper the typical features of different liquid grooves are presented, classified and analyzed on the base of our experimental data. The developed models confirm the dominant role of diffusion mechanisms.