Effect of the method of production of TiAl-based layered composite billets containing a ductile constituent on the structure of rolled sheets

The effect of the method of production of TiAl-based layered composite billets intended for hot rolling on the structure of rolled sheets is studied. The billets consist of (γ-TiAl + α₂-Ti₃Al)/ductile metallic constituent (DMC) materials, where DMC is a titanium alloy (VT1-00 or VT-9) or niobium (Nb1). The most promising methods for the upsetting of the billets after compacting by hot isostatic pressing have been chosen, and a pilot technology for the production of high-quality defectless 11-layer 3-mm-thick sheets using hot rolling to a total reduction of ～90% has been developed. Structural studies of the sheets indicate that the most promising materials for the DMC are a high-strength VT-9 alloy and, especially, high-melting-temperature niobium (Nb1). The strain resistance of Nb1 is comparable with that of a γ-TiAl-based superlight alloy, and diffusion processes between the layers of the related composite material are significantly slower than those in the layered composite materials with a DMC made of VT-9 and, especially, VT1-00.     

Mechanism of diagnostic significance of histidase release into the blood in lymphedema

We have analyzed retrospectively 200 case histories of either responders or nonresponders to extracorporeal lithotripsy (ECL). Using stochastic methods, we have identified 15 urolithiasis signs and symptoms essential for prediction of ECL outcomes. The data have been summarized with Bayes' methods and special software for personal computer have been developed facilitating the prognosis of ECT effectiveness. As shown by the results achieved in 330 urolithiasis patients treated in 1992-1996, the application of the computer raised the effectiveness of ECL from 82 to 94%.     

Transmutation of Metallic 99Tc into Ruthenium under Irradiation in High-Flux SM Reactor

Transmutation of ⁹⁹Tc upon irradiation of metallic technetium discs 6 mm in diameter and 0.3 mm thick in a neutron trap of high-flux SM reactor for 72.7 effective full-power days (100 mW thermal power) was studied. At a total neutron fluence of 8 × 10^{2 1} cm^{- 2} with the thermal component of 7.3 × 10^{2 1} cm^{- 2}, about 34% of ⁹⁹Tc is convereted to yield 0.8 g of ruthenium, which agrees within the limits of the determination error with the results of Monte-Carlo calculations. For ruthenium formed under these conditions to be used in practice without any restrictions, the target should be cooled for three years to decrease the ¹⁰³Ru activity and the decontamination factor with respect to ⁹⁹Tc should be about 3 × 10⁸.     

Study of rolling in helical rolls by mathematical simulation with the DEFORM 3D software package

A mathematical model is developed and adapted for lengthwise rolling in special-profile helical rolls using the Deform 3D software package. The metal flow in rolling in helical rolls is studied. The state of stress in the deformation zone is analyzed, and the rolling force is calculated as a function of the technological rolling parameters and the geometrical characteristics of the helical rolls.     

Texture,Structure, Mechanical Properties,and Deformability of MA2-1pch Magnesium Alloy Rolled Sheets Preliminarily Subjected to Direct Extrusion or Equal-Channel Angular Pressing and Annealing

The textural and structural evolution in MA2-1pch magnesium alloy sheets fabricated from initial workpieces after (1) hot direct extrusion or (2) equal-channel angular pressing performed by route B_c in four passes at 245°C and subsequent recrystallization annealing is investigated during warm rolling and subsequent uniaxial tension. The same sharp basal texture, but different structures with different average grain sizes and fractions of twinned grains form in sheets (made of two different workpieces) after warm rolling. Subsequent uniaxial tension arranges basal planes in the sheets made from workpiece 2 along prismatic directions. Modeling of texture within the framework of a thermoactivation model shows that the texture changes due to the activation of prismatic slip. Structural evolution during uniaxial tension in the sheets made of workpiece 2 is accompanied by more intense twinning than that in the sheets made of workpiece 1. These textural and structural changes are responsible for the enhanced mechanical properties and the deformability parameters of the sheets fabricated from workpiece 2.     

Economic efficiency of radionuclide neutron sources

Conclusion The method considered here enables us to make comparative economic estimates at the stages of development and application of RNS in the solution of the following problems: determining the limits of competitiveness of RNS based on different radionuclides, and also of RNS and other types of NS, determining the efficiency of utilization of specific RNS in comparison with conventional methods of performing the work, justifying the nomenclature of RNS manufacture with specific radionuclides, justifying the unit power and the number of simultaneously used RNS, estimating the efficiency of utilization of different combinations of RNS that have been used for a specified time and of new RNS, determining the efficiency of the successive use of RNS in different regions as their power is depleted, justifying the desirability of chemical reprocessing of the RNS used, etc.Today the method is used in practice for different purposes. In particular, an estimate has been prepared for the economic efficiency of the chemical reprocessing of californium RNS that have been taken out of service. The method has also been used for determining the limit of RNS power above which chemical reprocessing is effective. It has been shown that the chemical reprocessing makes it possible to increase the output of californium and reduce the cost of its manufacture. Researchers have also determined the economically advantageous interval of reprocessing with due regard for the decay of californium and the desirability of increasing the batches reprocessed.Translated from Atomnaya Énergiya, Vol. 58, No. 5, pp. 355–359, May, 1985.