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Sofia, Bulgaria

Sobczak J.J.,Poland Foundry Research Institute | Drenchev L.,Institute of Metal Science | Asthana R.,University of Wisconsin - Stout
International Journal of Cast Metals Research | Year: 2012

The effect of pressure on solidification structure formation in metal castings has been reviewed and explicitly expressed by thermodynamic relationships. In particular, pressure effects on phase diagrams, nucleation and growth, interfacial energy and diffusion coefficient are considered and analysed. Well known formulae and some new explicit relations are presented and discussed. Practical manifestations of the effect of pressure in casting structure formation are discussed. © 2012 W. S. Maney & Son Ltd.

Kuzmanov P.,Institute of Metal Science | Dimitrova R.,Institute of Metal Science | Lazarova R.,Institute of Metal Science | Cherepanov A.,RAS Institute of Theoretical and Applied Mechanics | And 4 more authors.
Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanoengineering and Nanosystems | Year: 2014

The influence of nanopowders on the structure and mechanical properties was investigated in castings of aluminium alloy AlSi7Mg, grey cast irons GG15 and GG25 and steel GX120Mn12. Mixtures of SiC, TiCN and Y2O3 nanopowders were used. These mixtures or nanocompositions were coated with Cu, Cr, Ni and Fe metal protectors in order to improve wetting of the metal melt. Introducing small amounts of nanocompositions (less than 0.1 wt%) into the melt was found to refine the microstructure and improve the mechanical properties of the castings. © IMechE 2013.

Sobczak J.J.,Poland Foundry Research Institute | Drenchev L.B.,Institute of Metal Science | Sobczak N.,Poland Foundry Research Institute | Asthana R.,University of Wisconsin - Stout
Materials Science Forum | Year: 2013

This paper discusses some theoretical aspects of design of ultralight metallic materials using analytical and heuristic arguments. Potential application of syntactic foams to obtain metalmatrix composites lighter than air is also analyzed. Carbon allotropes (fullerenes, colossal carbon tubes) and some non-carbon materials are considered as components of ultralight metal-matrix composites. Calculations for the size of fullerenes, number of atoms in their structure, and coating thickness required to produce ultralight composites are presented. It is concluded that 3D carbon molecules (fullerenes) and colossal carbon tubes are the most promising components to design ultralight metallic materials which can be lighter than air. © (2013) Trans Tech Publications, Switzerland.

Gidikova N.,Institute of Metal Science | Cias A.,AGH University of Science and Technology | Petkov V.,Institute of Metal Science | Madej M.,AGH University of Science and Technology | And 2 more authors.
Archives of Metallurgy and Materials | Year: 2014

Electrochemical chromium coatings on steel, modified with diamond nanoparticles (NDDS), were produced by detonation synthesis. Their particle size was from 10 to 50 nm. Galvanization conditions, current density, etc., concentration of NDDS, were studied in relation to the characteristics of the chromium coatings. The optimal conditions were determined to attain the maximal values of the physical and mechanical properties of the coating. Surface topography after wear testing was examined. Compared to unmodified chromium coating, microhardness of the surface increased to 1100 kg/mm2, wear resistance, expressed as % of mass loss, increased from 3 to 10 times. © 2014, Committee of Metallurgy. All rights reserved.

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