Effect of microstructure, deformation mode and rate on mechanical behaviour of electron-beam melted Ti-6Al-4V and Ti-1.5Al-6.8Mo-4.5Fe alloys

Two commercial costefficient titanium alloys—a lowalloyed α+βti–6Al–4V (mas.%) and a metastable βalloy ti–1.5Al–6.8Mo–4.5Fe melted with a single electronbeam cold hearth melting approach—are employed in a present study as program materials. the influence of microstructure formed by means of the subsequent thermomechanical and heat treatments on both the mechanical behaviour (evaluated by the deformation energy, UD) when tested using standard methods with different deformation rates and the ballistic resistance of plate materials is investigated.На прикладі двох промислових економно леґованих титанових стопів, — малолеґованого α + β-стопу ti–6Al–4V (мас.%) і метастабільного βстопу ti–1,5Al–6,8Mo–4,5Fe, — виготовлених одноразовим електроннопроменевим топленням з проміжною ємністю, вивчено вплив формованої за подальших (термомеханічного та термічного) оброблянь мікроструктури на механічну поведінку (виражену через енергію деформації UD) при випробуваннях з різними швидкостями деформації та балістичну стійкість.На примере двух промышленных экономно легированных титановых сплавов, — малолегированного α + βсплава Тi–6Al–4V (масс.%) и метастабильного βсплава ti–1,5Al–6,8Mo–4,5Fe, — приготовленных однократной электроннолучевой плавкой с промежуточной ёмкостью, изучено влияние формируемой при последующих (термомеханической и термической) обработках микроструктуры на механическое поведение (выраженное через энергию деформации UD) при ис пы таниях с разными скоростями деформации и баллистическую стойкость

Current limiting and negative differential resistance in indium oxide based ceramics

Indium oxide based ceramics with bismuth oxide addition were sintered in air in the temperature range 800-1300 ºC. Current-voltage characteristics of In2O3-Bi2O3 ceramics sintered at different temperatures are weakly nonlinear. After an additional heat treatment in air at about 200 ºC samples sintered at a temperature within the narrow range of about 1050-1100 ºC exhibit a current-limiting effect accompanied by low-frequency current oscillations. It is shown that the observed electrical properties are controlled by the grain-boundary barriers and the heat treatment in air at 200 ºC leads to the decrease in the barrier height. Electrical measurements, scanning electron microscopy and X-ray photoelectron spectroscopy results suggest that the current-limiting effect observed in In2O3-Bi2O3 may be explained in terms of a modified barrier model; the observed current-limiting effect is the result of an increase of barrier height with increasing electric field, due to additional oxygen absorption. It is found that In2O3-Bi2O3-Co3O4-Cr2O3 ceramic exhibits current-voltage characteristics with negative differential resistance due to Joule micro heating.This study was performed in part in the frames of the project SEP-2003-C02-42821, CONACYT, México. Funding from the Royal Society, United Kingdom (2007R1/R26999) is gratefully acknowledged

Prognosis of Elevated Serum Ferritin in Allogeneic-HCT

Introduction: Serum ferritin was demonstrated to be a useful tool to predict the risk in patients who undergo hematopoietic stem cell transplantation (HCT). Still it is not clear if its predictive value solely represents iron overload (IO) and published results are sometimes contradictory. So the objective of present study was to determine relationship between elevated pre-HCT serum ferritin levels, morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HCT) on one side, and its correlations with various risk indexes which were developed recently to predict outcomes after allo-HCT on the other side. Patients and Methods: In this retrospective study we have reviewed medical records of one hundred six consecutive patients (52 males and 54 females), with a median age of 32 years (range, 5 to 60), who underwent allo-HCT with unmanipulated grafts between Jan 2013 and Dec2014. We retrieved pre-allo-HCT serum ferritin levels and also calculated risk indexes before HCT. The incidence of complications and outcomes after allo-HCT was assessed. The median follow-up period was 12 (range, 4-27) months after allo-HCT. Results: We have determined a cuttoff ferritin level of 500 ng/mL for early complications and 737 for outcomes. We found increased incidence of number of febrile neutropenic episodes (P =0.02), number of bacterial infection episodes (P =0.009), pneumonias (P =0.039), slower period of neutrophil engraftment (P=0.032), demand for multiple red blood cell (RBC) transfusions (P =0.002) within 100 days post transplantation. A significant association was found between pre-transplant ferritin concentrations and different risk indexes; European Group for Blood and Marrow Transplantation (EBMT) risk score (P=0.001), Hematopoietic cell transplantation comorbidity index (HCT-CI) (P=0.003), Pre-transplant Assessment of Mortality (PAM) score (P=0.007) and disease risk (DR) (P =0.037). Conclusion: On the one hand we did confirmed that even moderate serum ferritin elevation is associated with increased incidence of infections, slower period to engraftment and increasing demand of RBC units transfusions, but strong correlation with pre-transplant indexes that take into account disease risk raises the question if IO is the only factor that adversely affect the outcome of HCT in patients with increased ferritin. This should be studied in prospective trials

Electron Beam Cold Hearth Melted Titanium Alloys and the Possibility of Their Use as Anti-Ballistic Materials

Three commercial titanium alloys: two-phase α+β Ti-6Al-4V (low alloyed), and T110 (Ti-5.5Al-1.5V-1.5Mo-4Nb-0.5Fe, higher-alloyed), and β-metastable Ti-1.5Al-6.8Mo-4.5Fe were melted using EBCHM approach in the form of 100 mm in diameter ingots with the weight of about 20 kg each. After 3D hot pressing at single β-field temperatures ingots were rolled at temperatures below β-transus onto plates with thickness varying from 3 mm to 25 mm. Different heat treatments, including annealing at α+β or β-field temperatures, and special strengthening Surface Rapid Heat Treatment (SRHT) which after final aging provided special gradient microstructure with a hardened surface layer over ductile basic core, were employed. Mechanical properties were studied with tensile and 3-point flexure tests. It was established that the best combination of tensile strength and ductility in all alloys studied was obtained after SRHT, whereas at 3-point flexure better characteristics were obtained for the materials annealed at temperatures of (α+β)-field. At the same time, ballistic tests made at a certified laboratory with different kinds of ammunition showed essential superiority of plates having upper layers strengthened with SRHT. The effect of microstructure of the alloys, plate thickness and type of used ammunition on ballistic resistance is discussed

Electron Beam Cold Hearth Melted Titanium Alloys and the Possibility of Their Use as Anti-Ballistic Materials

Three commercial titanium alloys: two-phase α+β Ti-6Al-4V (low alloyed), and T110 (Ti-5.5Al-1.5V-1.5Mo-4Nb-0.5Fe, higher-alloyed), and β-metastable Ti-1.5Al-6.8Mo-4.5Fe were melted using EBCHM approach in the form of 100 mm in diameter ingots with the weight of about 20 kg each. After 3D hot pressing at single β-field temperatures ingots were rolled at temperatures below β-transus onto plates with thickness varying from 3 mm to 25 mm. Different heat treatments, including annealing at α+β or β-field temperatures, and special strengthening Surface Rapid Heat Treatment (SRHT) which after final aging provided special gradient microstructure with a hardened surface layer over ductile basic core, were employed. Mechanical properties were studied with tensile and 3-point flexure tests. It was established that the best combination of tensile strength and ductility in all alloys studied was obtained after SRHT, whereas at 3-point flexure better characteristics were obtained for the materials annealed at temperatures of (α+β)-field. At the same time, ballistic tests made at a certified laboratory with different kinds of ammunition showed essential superiority of plates having upper layers strengthened with SRHT. The effect of microstructure of the alloys, plate thickness and type of used ammunition on ballistic resistance is discussed

The model of upstream investment portfolio in the mature regions

Portfolio models can serve as an assessment tool for the optimal assignment of capital between the potential investment projects in the various conditions for upstream companies. This process is crucial for any company if it wants to balance the short-term goals and seeks to maximize long-term value of the company. The paper aims to present a practical model of forming oil upstream company’s portfolio. The unique feature of this model is an individual approach to investment plan forming in a context of three types of projects: Exploration, oil production and infrastructure projects. This is due to the individual approach which is used for comparison of all projects by using of universal set of indicators. Suggested model uses the multi-criteria selection mechanism by means of aggregating the key estimating indicators into the final project rank score. In that way the task of forming investment project’s portfolio of upstream company is a linear programming problem that is solved by simplex method. In the paper the model forms consolidated investment portfolio that takes into account decision makers’ preferences in setting of limits for resources. © 2019, Econjournals. All rights reserved

The assessment of the development of foreign trade relations of Russia based on the cointegration analysis

The methods of cointegration analysis and the Vector error correction model (VECM) were used in the study of the peculiarities of Russian foreign economic relations with the main partner countries in the sectoral context. As a result of the research, reliable models of cointegration interrelations were obtained, which allowed us to reveal certain patterns of trade development of the selected group of countries. The obtained cointegrating coefficients made it possible to estimate the speed of recovery of trade links that were disrupted due to external influences. This information about the resistance of international trade ties is important for economic analysis and forecasting. © IAEME Publication