2nd Edition of World Nanotechnology Conference

April 27-29, 2020 | Baltimore, USA

Crowne Plaza Hotel Baltimore Dowtown –
Inner Harbor, 105 W Fayette Street
Baltimore, MD 21201 USA
Phone : 1 (702) 988 2320
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Email: worldnano@magnus-group.org
April 27-29, 2020 | Baltimore, USA

Viktor Novikov

Speaker for Nanotechnology Conferences  2020
Viktor Novikov
National University of Science and Technology, Russia
Title : Metals property changes under effect of vacancy-cluster structures

Abstract:

The experimental results analysis of a metals property changes under vacancy-cluster structure effects are shown. Two technological approaches of such structures obtaining are considered. The first is a nanopowders compaction under high (up to 5GPa) hydrostatic compression, on example of a Ni nanopowder (70nm). The second is the Al and Pb crystallization under the high-intensity plastic deformation [ε?= (102-104) sec-1] (?IPD) conditions on the "solid-liquid" boundary in the centrifugal casting machine with rotary speed up to 2000 rpm. Using the method of atomic force microscopy (AFM), 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. Discussed the physical model of a new substructure formation within the metals in the form of vacancy cluster tubes, obtained in the process of high-intensive plastic deformation (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 high-intensive plastic deformation (HIPD) range about [ε′ = (102–104) 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) re-crystallization. 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 [ε′ = (102–104) sec-1] of the crystallized metal melt solidified phase. Since the grain sizes at the crystallized phase initially comprise around tens of nano-meters (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 statescharacteristic of non-equilibrium open systems. Discussed the physical model of a metals vacancy-cluster structures formation  at  high  hydrostatic nanopowders compression (up to 5 GPa) and high-intensity plastic deformation (HIPD) at the stage of Al and Pb alloys mass crystallization during centrifugation. Conclusion of the article is that the high-intensity plastic deformation (?IPD) at the melt crystallization stage against a background of high stationary nonequilibrium vacancies concentration brings to the new type    of the elements structure formation - vacancy cluster tubes (VCT). A comparative analysis of mechanical, magnetic and superconducting properties changes for structured metals introduced.

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