Self-propagating waves of crystallization in metallic glasses
Self-propagating thermal waves of the amorphous-crystalline transformation in Fe-based metallic glasses, obtained by melt spinning, were observed using a high-speed infrared camera and reported here. Some experimental results are also reported concerning oscillating waves in the CuTi glassy foils. The thermal characteristics and wave propagating velocities, as well as the microstructure and atomic structure transformations, were studied. A comparison of the results with exothermic reaction waves and explosive crystallization shows that the self-propagating waves in metallic glasses are slower and less violent than classical explosive crystallization in deposited films; thus, we suggest naming this phenomenon “soft explosive crystallization.” The experimental data were confirmed by molecular dynamics simulation of the crystallization phenomenon.
The results of the study of radiation-induced strengthening and microstructure evolution in the 0Kh18N10T austenitic stainless steel irradiated by neon ions (with energy of 230 MeV) and neutrons (En > 0.1 MeV) are presented. The experiments were performed in an inner beam of an U-400 cyclotron in Dubna and in an EWA reactor (Institute of Atomic Energy, Swerk, Poland). The dependence of the mechanical properties on the dose of irradiation-induced damage was determined. Changes in microstructure are studied by TEM, and the density of the aggregates of irradiation-induced defects was determined as a function of the dose. The data obtained are discussed in terms of mechanical properties and microstructure characteristics.
Binary Al–Ni, Al–Mg and ternary Al–Mg–Ni alloys containing various dispersions and volume fraction of second-phase particles of crystallisation origin were compressed in a temperature range of 200–500 °C and at strain rates of 0.1, 1, 10, 30 s−1 using the Gleeble 3800 thermomechanical simulator. Verification of axisymmetric compression tests was made by finite-element modelling. Constitutive models of hot deformation were constructed and effective activation energy of hot deformation was determined. It was found that the flow stress is lowered by decreasing the Al3Ni particle size in case of a low 0.03 volume fraction of particles in binary Al–Ni alloys. Intensive softening at large strains was achieved in the alloy with a 0.1 volume fraction of fine Al3Ni particles. Microstructure investigations confirmed that softening is a result of the dynamic restoration processes which were accelerated by fine particles. In contrast, the size of the particles had no influence on the flow stress of ternary Al–Mg–Ni alloy due to significant work hardening of the aluminium solid solution. Atoms of Mg in the aluminium solid solution significantly affect the deformation process and lead to the growth of the effective activation energy from 130–150 kJ/mol in the binary Al–Ni alloys to 170–190 kJ/mol in the ternary Al–Mg–Ni alloy.
The multicomponent nitride coatings from TiZrNbAlYCr high entropy alloy (HEA) were fabricated using the vacuum-arc method. The effect of nitrogen pressure on the crystallite size, elemental and phase composition of (TiZrNbAlYCr) N coatings was investigated. A bias voltage applied to the substrate during the deposition process was -200 V. The partial nitrogen pressure was 0.05 Pa, 0.27 Pa, and 0.5 Pa. Body-centered cubic (BCC) lattice with crystallites of 15 nm in size was formed at the lowest pressure. An increase in the pressure led to the formation of the two-phase structure: BCC phase with crystallite size of 15 nm and face-centered cubic (FCC) phase with crystallite size of about 3.5 nm. The same two-phase state was found in coatings fabricated at 0.5 Pa, while the mean crystallite size was 7 nm. The maximum hardness of the deposited coatings was about 47 GPa.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.