Simulation of the combined process “helical rolling-pressing” in the software package Simufact. Forming

This work is devoted to the simulation of new energy-saving combined process "helical rolling-pressing" in program Simufact Forming. During the simulation were studied the main parameters of stress-strain state and microstructure. The variation of the main technological parameters showed that the influence of the heating temperature of the workpiece plays a significant role in the degree of grain grinding. While the speed of deformation, allowed by the mill design limits, has no significant effect on the microstructure

Simulation of the combined process “helical rolling-pressing” in the software package Simufact. Forming

This work is devoted to the simulation of new energy-saving combined process "helical rolling-pressing" in program Simufact Forming. During the simulation were studied the main parameters of stress-strain state and microstructure. The variation of the main technological parameters showed that the influence of the heating temperature of the workpiece plays a significant role in the degree of grain grinding. While the speed of deformation, allowed by the mill design limits, has no significant effect on the microstructure

OBTAINING OF UFG STRUCTURE OF ZR-1% NB ALLOY BY RADIAL-SHEAR ROLLING

An overview of the prospects for the development of nuclear technologies and the conclusion of the relevant requirements for advanced structural materials, their classification and features were described. In order to obtain a bar with a modified radiation-resistant outer layer, an experiment on radial-shear rolling of the Zr-1% Nb alloy in conditions favorable for the UFG structure formation was conducted. In the process of radial-shear rolling of round bars along the route 37 mm → 20 mm in diameters with a total deformation of ≈ 70 %, a microstructure of submicron size was obtained. The nature of the microstructure is equiaxed with mainly high-angle boundaries and large crystallographic misorientation of the grains that is the most promising from the point of view of radiation resistance

HOW GAP DISTANCE BETWEEN GOLD NANOPARTICLES IN DIMERS AND TRIMERS ON METALLIC AND NON-METALLIC SERS SUBSTRATES CAN IMPACT SIGNAL ENHANCEMENT

The impact of variation in the interparticle gaps in dimers and trimers of gold nanoparticles (AuNPs), modified with Raman reporter (2-MOTP), on surface-enhanced Raman scattering (SERS) intensity, relative to the SERS intensity of a single AuNP, is investigated in this paper. The dimers, trimers, and single particles are investigated on the surfaces of four substrates: gold (Au), aluminium (Al), silver (Ag) film, and silicon (Si) wafer. The interparticle distance between AuNPs was tuned by selecting mercaptocarboxylic acids of various carbon chain lengths when each acid forms a mixed SAM with 2- MOTP. The SERS signal quantification was accomplished by combining maps of SERS intensity from a Raman microscope, optical microscope images ( 100), and maps/images from AFM or SEM. In total, we analysed 1224 SERS nanoantennas (533 dimers, 648 monomers, and 43 trimers). The average interparticle gaps were measured using TEM. We observed inverse exponential trends for the Raman intensity ratio and enhancement factor ratio versus gap distance on all substrates. Gold substrate, followed by silicon, showed the highest Raman intensity ratio (9) and dimer vs. monomer enhancement factor ratio (up to 4.5), in addition to the steepest inverse exponential curve. The results may help find a balance between SERS signal reproducibility and signal intensity that would be beneficial for future agglomerated NPs in SERS measurements. The developed method of 3 to 1 map combination by an increase in image transparency can be used to study structure–activity relationships on various substrates in situ, and it can be applied beyond SERS microscopy

DEVELOPMENT OF ALTERNATIVE METHOD FOR MANUFACTURING STRUCTURAL ZIRCONIUM ELEMENTS FOR NUCLEAR ENGINEERING

irconium is used as a structural material for use in aggressive environments, including the core of nuclear reactors. The traditional technology of manufacturing the structural elements of zirconium nuclear reactors is characterized by a long technological process and a significant amount of waste in the form of metal shavings. The paper presents the results of an alternative technology, spark plasma sintering, for manufacturing zirconium products. A complex of microstructural and mechanical studies of the obtained samples was carried out according to the ASTMB-351 standard. The sintering of zirconium powder and options for subsequent processing by various methods, including non-standard ones such as radial shear rolling, are justified. Keywords: zirconium; powder metallurgy; spark plasma sintering; microstructure; rheological; dilatometric studie

Investigation of the Influence of Hot Forging Parameters on the Closing Conditions of Internal Metallurgical Defects in Zirconium Alloy Ingots

In this article, we present research results on the closing conditions of internal metallurgical discontinuities during the hot elongation operation of a Zr-1%Nb alloy ingot using physical and numerical modeling. Research on the influence of thermal and deformation parameters of elongation operations on the rheological behavior of a Zr-1% Nb alloy was conducted using the Gleeble 3800 metallurgical process simulator. Modeling of the influence of thermal–mechanical parameters of hot elongation operations in combinations of rhombic and flat anvils on the closure of metallurgical discontinuities was performed with the help of the FORGE®NxT 2.1 program. Based on the results of the research, recommendations were made regarding forging elongation technology and the geometry of working tools in order to ensure the closure of metallurgical discontinuities during hot elongation operations of Zr-1% Nb alloy ingots

EFFECTIVE TECHNOLOGIES OF SEVERE PLASTIC DEFORMATION

Creation of new structural materials with new unique properties of metal remains one of the urgent tasks of modern materials science. In practice, it is possible to improve the properties of existing structural materials by grinding their structure to an ultra-fine-grained state. At the moment, one of the promising ways to obtain an ultra-fine-grained structure is the severe plastic deformation method (SPD). Most of the currently existing methods of implementation of the SPD have not been used in the real industrial sector due to the existing in this method of deformation of the disadvantage, which is the discreteness, i.e. the inability to process products of relatively long length and the need for a large number of processing cycles. And this determines the economic inexpediency of the introduction of this method in production. To solve the problem of introduction of the technology of production of ultra-fine-grained materials by SPD methods, we have developed a number of combined technologies of deformation, allowing to obtain rods of rectangular and circular cross-section of ferrous and non-ferrous metals with ultra-fine-grained structure. These processes include the following combined methods: "rolling-ECAP", “ECAP-drawing” "screw rolling-ECAP". As a result of numerous laboratory studies, to study the effect of the proposed methods of deformation on the microstructure evolution of various structural materials and change their properties, it was proved that the combined processes "rolling-ECAP" and "screw rolling – ECAP" have undeniable advantages over conventional equal-channel angular pressing, both in terms of more intensive grinding of grain and higher mechanical characteristics of the deformable metal in one cycle of deformation, and in terms of the possibility of obtaining long blanks