Влияние вакансионно-кластерных структур на свойства металлов

Abstract

The paper carries out the analysis of the experimental results on the metals property changes under vacancy-cluster structure effects. We have considered two technological approaches of such structures obtaining. The first one is a nanopowders compaction under high (up to 5 GPa) hydrostatic compression, on example of a Ni nanopowder (70 nm). The second one is the Al and Pb crystallization under the high-intensity plastic deformation [ e ′ = (10 2 –10 4 ) sec –1 ] ( Н IPD) conditions on the solid and liquid boundary in the centrifugal casting machine with rotary speed up to 2000 rpm. Using the method of atomic force microscopy, vacancy cluster tubes (VCT) with average diameters of 39 nm for Al and 25 nm for Pb have been detected in the crystallized volume of Al and Pb metals. The paper discusses the physical model of a new substructure formation within the metals in the form of vacancy cluster tubes obtained in the process of HIPD during the process of mass crystallization of Al and Pb and the changes in the mechanical, magnetic, and superconducting properties of the above metals, which followed this process. During Al and Pb crystallization under HIPD range about [ e ′ = (10 2 –10 4 ) sec –1 ] with specially selected modes of metals crystallization in high-speed centrifugal casting machine, the special conditions are being created to achieve the dimensional effect of dynamic (shifting) recrystallization. Shifting deformation during centrifugal crystallization caused primarily by a large incline of the temperature field from the periphery (relative to the cold wall of the rotor) to the molten central part of the rotor. The difference in the angular velocities of the already frozen part of the metal (adjacent to the outer surface of the rotor wall) and the central part where the metal still remains in the molten state leads to a high-intensity deformation [ e ′ = (10 2 –10 4 ) sec –1 ] of the crystallized metal melt solidified phase. Since the grain sizes at the crystallized phase initially comprise around tens of nanometers (approximately crystal nucleation size), it becomes possible to achieve the dimensional effect of the dynamic re-crystallization of a “nanocrystalline” solidified metal at high shift of strain velocities. The “non-equilibrium vacancies” formed this way condense into vacancy clusters, which are formed in the centrifugal force field in the form of vacancy-shaped cluster tubes stretched out to the center of rotation of the rotor. The process proceeds under conditions far from the equilibrium in comparison with the usual crystallization of the metal from the melt. Such processes can lead to the formation of highly ordered non-equilibrium states characteristic of non-equilibrium open systems.