Spark Plasma Sintering for high-speed diffusion welding of the ultrafine grained near-a Ti-5Al-2V alloy with high strength and corrosion resistance for nuclear engineering

The paper demonstrates the prospects of Spark Plasma Sintering (SPS) for the high-speed diffusion welding of the high-strength ultrafine-grained (UFG) near-a Ti-5Al-2V alloy. The effect of increased diffusion welding intensity in the UFG Ti alloys is discussed also. The welds of the UFG near-a-Ti-5Al-2V alloy obtained by SPS are featured by high density, strength, and corrosion resistance. The rate of weld sealing in the UFG alloys has been shown to depend on the heating rate non-monotonously (with a pronounced maximum). At the stage of continuous heating and isothermic holding, the kinetics of the weld sealing was found to be determined by the exponential creep rate, the intensity of which in the coarse-grained (CG) alloys is limited by the diffusion rate in the crystal lattice whereas in the UFG alloys it is limited by the grain boundary diffusion rate.Comment: 62 pages, 3 tables, 24 figures, 61 reference

Investigation of Microstructure and Corrosion Resistance of Ti-Al-V Titanium Alloys Obtained by Spark Plasma Sintering

The research results of the microstructure and corrosion resistance of Ti and Ti-Al-V Russian industrial titanium alloys obtained by spark plasma sintering (SPS) are described. Investigations of the microstructure, phase composition, hardness, tensile strength, electrochemical corrosion resistance and hot salt corrosion of Ti-Al-V titanium alloy specimens were carried out. It was shown that the alloy specimens have a uniform highly dense microstructure and high hardness values. The studied alloys also have high resistance to electrochemical corrosion during tests in acidic aqueous solution causing the intergranular corrosion as well as high resistance to the hot salt corrosion. The assumption that the high hardness of the alloys as well as the differences in the corrosion resistance of the central and lateral parts of the specimens are due to the diffusion of carbon from the graphite mold into the specimen surface was suggested.Comment: 28 pages, 3 tables, 13 figures, 61 reference

Telomere Shortening Sensitizes Cancer Cells to Selected Cytotoxic Agents: In Vitro and In Vivo Studies and Putative Mechanisms

or telomere shortening resulting from inhibition of telomerase activity. In addition, the characteristics and mechanisms of sensitization to cytotoxic drugs caused by telomerase inhibition has not been elucidated in a systematic manner. mouse model. The putative explanation underlying the phenotype induced by telomere shortening may be related to changes in expression of various microRNAs triggered by telomere shortening.To our best knowledge this is the first study characterizing the relative impact of telomerase inhibition and telomere shortening on several aspects of cancer cell phenotype, especially related to sensitivity to cytotoxic drugs and its putative mechanisms. The microRNA changes in cancer cells upon telomere shortening are novel information. These findings may facilitate the development of telomere based approaches in treatment of cancer

Using Process Mining and Control Charts to Improve the Reliability of Road Freight Transportation

Management of a process assumes the availability of metrics to reflect its status. During road freight transportation, nowadays various sensors provide you with a full picture of what is happening with the vehicle and freight. Accordingly, in case of deviation from the specified transportation parameters, the company's CEO can exercise his/her management to adjust the transportation process. However, the influence of the human factor on the reliability of transportation is still considerable. So, methods and approaches are required to assess actions and business activities of personnel quickly and efficiently. It is currently relevant for the transportation process not only to collect data on driver behavior, but also to deeply analyze the behavior of operators of the fleet management information system

Key factors for reducing live poultry losses during transportation

The results of this study on the loss of live poultry at various stages of delivery from the farm to the processing plant by road are given. A factor analysis of the reasons for the loss of livestock delivered from the farm to the processing plant was carried out. The dependencies of livestock losses on loading delays and the duration of the movement of the loaded poultry farm to the processing plant were established. Methodological recommendations for rationing the number of injuries observed during delivery were developed. The study of losses of live birds during delivery to the processing plant from the density of stocking in shipping boxes was carried out; the economic and mathematical model for optimizing the landing of live birds in shipping boxes was proposed. The calculation of the economic impact of the implementation of the results of the study is given

INCREASED EFFICIENCY AND RELIABILITY OF MAINTANANCE OF MASS PASSENGER FLOW WITH THE REGULAR ROUTE NETWORK OF CITY TRANSPORT

This study is aimed at improving the methods of carriage of passengers by urban transport to improve its reliability and efficiency. It can be achieved by forming back-up bus routes within the existing regular route network for servicing mass passenger-flows. This study theoretically substantiates the impact of back-up bus routes in the current regular route network on the reliability and efficiency of the transport process. Mathematical models of reservation of regular route network and the assessment of the reliability of passenger transport using different reservation schemes are suggested. Methodological recommendations on the formation of passenger traffic on back-up bus routes and cost reduction on its maintenance, by managing the route speed depending on the loading of the city road network, have been developed. Technical and economic evaluation was conducted to the developed methodological toolkit

Method of W-Ni-Fe Composite Spherical Powder Production and the Possibility of Its Application in Selective Laser Melting Technology

For the first time, a powder of W-5Ni-2Fe composition with spherical particles from 15 to 50 microns and a tungsten grain size from 0.5 to 3 microns was obtained using a new technological approach, developed by the authors, based on plasma spheroidization of powder granules made from nanoparticles synthesized in a plasma chemical process. The possibility of using the obtained spheroidized powder W-5Ni-2Fe in the process of selective laser melting (SLM) has been proved. The microstructure, physical, and mechanical characteristics of experimental samples made using SLM technology from the produced W-5Ni-2Fe powder have been studied. The results of the performed studies have shown that the microstructure of experimental samples is extremely dependent on the parameters of the SLM process. The precise choice of the SLM process mode made it possible to obtain a homogeneous structure of experimental samples of tungsten heavy alloy (WHA), with a tungsten grain size of about 1–2 microns, which is much smaller than the tungsten grain size in traditional heavy alloys. This creates prerequisites for increasing the strength characteristics of parts of complex shapes made by the SLM method from such powders. The maximum values of density and hardness of experimental samples obtained in the conducted studies are not worse than the values of samples obtained using traditional liquid-phase sintering technology. It is determined that the main problem of SLM powder W-5Ni-2Fe during investigation is the heterogeneity of the microstructure of massive samples and the formation of micropores and microcracks

Method of W-Ni-Fe Composite Spherical Powder Production and the Possibility of Its Application in Selective Laser Melting Technology

For the first time, a powder of W-5Ni-2Fe composition with spherical particles from 15 to 50 microns and a tungsten grain size from 0.5 to 3 microns was obtained using a new technological approach, developed by the authors, based on plasma spheroidization of powder granules made from nanoparticles synthesized in a plasma chemical process. The possibility of using the obtained spheroidized powder W-5Ni-2Fe in the process of selective laser melting (SLM) has been proved. The microstructure, physical, and mechanical characteristics of experimental samples made using SLM technology from the produced W-5Ni-2Fe powder have been studied. The results of the performed studies have shown that the microstructure of experimental samples is extremely dependent on the parameters of the SLM process. The precise choice of the SLM process mode made it possible to obtain a homogeneous structure of experimental samples of tungsten heavy alloy (WHA), with a tungsten grain size of about 1–2 microns, which is much smaller than the tungsten grain size in traditional heavy alloys. This creates prerequisites for increasing the strength characteristics of parts of complex shapes made by the SLM method from such powders. The maximum values of density and hardness of experimental samples obtained in the conducted studies are not worse than the values of samples obtained using traditional liquid-phase sintering technology. It is determined that the main problem of SLM powder W-5Ni-2Fe during investigation is the heterogeneity of the microstructure of massive samples and the formation of micropores and microcracks

Effect of Sc, Hf, and Yb Additions on Superplasticity of a Fine-Grained Al-0.4%Zr Alloy

This research was undertaken to study the way deformation behaves in ultrafine-grained (UFG)-conducting Al-Zr alloys doped with Sc, Hf, and Yb. All in all, eight alloys were studied with zirconium partially replaced by Sc, Hf, and/or Yb. Doping elements (X = Zr, Sc, Hf, Yb) in the alloys totaled 0.4 wt.%. The choice of doping elements was conditioned by the possible precipitation of Al3X particles with L12 structure in the course of annealing these alloys. Such particles provide higher thermal stability of a nonequilibrium UFG microstructure. Initial coarse-grained samples were obtained by induction casting. A UFG microstructure in the alloys was formed by equal-channel angular pressing (ECAP) at 225 °C. Superplasticity tests were carried out at temperatures ranging from 300 to 500 °C and strain rates varying between 3.3 × 10−4 and 3.3 × 10−1 s−1. The highest values of elongation to failure are observed in Sc-doped alloys. A UFG Al-0.2%Zr-0.1%Sc-0.1%Hf alloy has maximum ductility: at 450 °C and a strain rate of 3.3 × 10−3 s−1, relative elongation to failure reaches 765%. At the onset of superplasticity, stress (σ)–strain (ε) curves are characterized by a stage of homogeneous (uniform) strain and a long stage of localized plastic flow. The dependence of homogeneous (uniform) strain (εeq) on test temperature in UFG Sc-doped alloys is increasing uniformly, which is not the case for other UFG alloys, with εeq(T) dependence peaking at 350–400 °C. The strain rate sensitivity coefficient of flow stress m is small and does not exceed 0.26–0.3 at 400–500 °C. In UFG alloys containing no Sc, the m coefficient is observed to go down to 0.12–0.18 at 500 °C. It has been suggested that lower m values are driven by intensive grain growth and pore formation in large Al3X particles, which develop specifically at an ingot crystallization stage

Investigation of Microstructure and Corrosion Resistance of Ti-Al-V Titanium Alloys Obtained by Spark Plasma Sintering

The research results of the microstructure and corrosion resistance of Ti and Ti-Al-V Russian industrial titanium alloys obtained by spark plasma sintering (SPS) are described. Investigations of the microstructure, phase composition, hardness, tensile strength, electrochemical corrosion resistance and hot salt corrosion of Ti-Al-V titanium alloy specimens were carried out. It was shown that the alloy specimens have a uniform highly dense microstructure and high hardness values. The studied alloys also have high resistance to electrochemical corrosion during tests in acidic aqueous solution causing the intergranular corrosion as well as high resistance to the hot salt corrosion. The assumption that the high hardness of the alloys as well as the differences in the corrosion resistance of the central and lateral parts of the specimens are due to the diffusion of carbon from the graphite mold into the specimen surface was suggested