High-temperature Background Research Articles

Anelasticity of Mg-Mn and Mg-Gd alloys

Anelastic relaxation at sub-resonance frequency (from 0.01 to 100 Hz), temperature (from 0 to 450°C) and amplitude (ε0 from 5×10−5 to 10−3) range in binary Mg-0.8 wt%Mn (0.36 at%) and Mg-2 wt%Gd (0.31 at%) in as-extruded and annealed states was experimentally studied and analyzed, to characterize acting thermally activated and structural relaxation effects. Activation parameters for thermally activated anelastic effect and structural studies suggest that it is the grain boundary relaxation with dominating large angle boundaries, while the high-temperature background is mainly controlled by dislocations sliding. Pseudo peak at ∼290 °C (Mg-Mn) and ∼410 °C (Mg-Gd) is the result of the recrystallization process in the as-extruded samples, which indicates that the addition of Gd restricts the recrystallization of Mg compared with the addition of Mn. Analysis of amplitude dependencies of internal friction in the frames of Granato and Lücke approach suggests higher density of movable dislocations in as-extruded Mg-Mn alloy.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

On the Vacancy Nature of the High-Temperature Background of Internal Friction in Solids

On the Vacancy Nature of the High-Temperature Background of Internal Friction in Solids

Study of viscoelastic transition in heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system

Heat-resistant materials used, for example, in aircraft parts, are exposed to high temperatures and are heated under the impact of variable external forces. At a certain point in time, the material that first experienced a small deformation ceases to be simply elastic and graduates into a viscoelastic state. Microyield thus developed in the material, subsequently leads to the creep. We present the results of studying the microyield in a heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system. A high-temperature background of the internal friction was studied by mechanical spectroscopy. It is shown that the transition of the alloy from an elastic to a viscoelastic state proceeds in two stages and is accompanied by microyield resulted from the dislocation movement. The first and second activation energies of the high-temperatureinternal friction background are determined for the state of the material under consideration. An expression for calculating the transition temperature is derived. The results obtained can be used in the study of the states of heat-resistant, high-temperature and structured materials, as well as amorphous metals and alloys.

A High-Precision Temperature Measurement Method Through Correcting Reflected Radiation Under High-Temperature Background

In this paper, a high precision correction method for temperature measurement errors due to reflected radiation under high temperature background is reported by applying calibration experiments. The correction theory governing the temperature measurement errors caused by reflected radiation is derived in principle, and the physical field model of temperature measurement is established for a ceramic blade in a high temperature furnace. The temperature measurement errors before and after the correction of the reflected radiation are analyzed through simulations, and the reflected radiation in the temperature measurement environment of the blade is calibrated. The experimental results show that the errors of monochromatic and colorimetric temperature measurements are decreased from 13.5% and 7.5% to 0.3% and 0.5%, respectively. The results indicate that the proposed method can significantly decrease the temperature measurement errors caused by reflected radiation.

Recrystallization in Ti5553 and Ti4733 detected by mechanical spectroscopy

This paper proposes a new way to detect recrystallization in beta-metastable alloys Ti5553 and Ti4733. Samples of these alloys were cold rolled and thermally treated. Internal friction was measured during heat cycles using a torsion pendulum. A correlation between recrystallization and sharp peak in internal friction specra was shown. The mechanism of dissolution of alpha phase triggering the recrystallization is proposed. In subsequent temperature cycles, the internal friction high temperature background decreases and stabilizes after three cycles. This is attributed with secondary recrystallization leading to grain growth. The size of the grains for different recrystallization time and temperature was measured and is coherent with the mechanical spectroscopy results. This result tends to prove that internal friction measurement can be used to optimize recrystallization treatment in beta metastable titanium alloys.

Multi-spectral radiation thermometry based on an Alpha spectrum-LM algorithm under the background of high temperature and intense reflection.

In order to meet the needs of multi-spectral radiation temperature measurement under high temperature background, this paper studies the problems of reflected radiation interference and spectral emissivity difficult to obtain in high temperature and intense reflection environment. First, using discrete triangular surface elements and radiation angle coefficients, an analysis model of high temperature background reflected radiation is constructed to describe the variation characteristics of high temperature background reflected radiation. Secondly, the least squares support vector machine (LSSVM) is optimized by particle swarm optimization (PSO) algorithm, and an emissivity model identification algorithm based on Alpha spectrum-Levenberg Marquarelt (LM) algorithm is proposed, which has stronger applicability and accuracy than existing emissivity model identification methods. Finally, the high temperature background radiation and the emissivity model are combined to construct and solve the multi-spectral target equation, so as to realize the reflected radiation error correction and radiation temperature measurement under the high temperature and intense reflection background. The simulation and experimental comparison with the existing methods show that the temperature measurement error of the radiation temperature measurement method proposed in this paper is below 9.5K, which can effectively correct the reflected radiation error and further improve the temperature measurement accuracy.

Damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders with different thicknesses and preparation directions

PurposeThis study aims to experimentally assess the effect of thickness and preparation direction on the damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders.Design/methodology/approachSn58Bi and Sn3.0Ag0.5Cu solder strips with different thicknesses were prepared from the bulk in longitudinal and horizontal directions, and the ratio of loss modulus and storage modulus of the samples was measured by the dynamic mechanical analysis method as the index of damping properties.FindingsSn58Bi and Sn3.0Ag0.5Cu solders exhibited viscoelastic relaxation, and their damping properties decreased with decreasing thickness. The damping properties of both solders had no obvious difference in longitudinal and horizontal directions. Sn58Bi has a more obvious high-temperature damping background than Sn3.0Ag0.5Cu solder. In addition, compared with Sn58Bi solder, Sn3.0Ag0.5Cu solder had an obvious internal friction peak, which moved toward high temperature with increasing frequency. The activation energies of Sn58Bi solder with a thickness of 0.5 mm at the longitudinal and horizontal directions were 0.84 and 0.67 eV, respectively, which were 0.39 and 0.53 eV, respectively, for the Sn3.0Ag0.5Cu solder.Originality/valueThe damping properties of Sn58Bi and Sn3.0Ag0.5Cu solder decreased with decreasing thickness, while their damping properties changed insignificantly when they were prepared from different directions. The internal friction peak of Sn3.0Ag0.5Cu solder moved to higher temperatures with increasing frequency.

Internal Friction and Creep of Titanium Aluminides with Different Microstructure

AbstractATi-46.5 Al-4 (Cr, Nb, Ta, B) alloy (at.%) with different microstructures (fine-grained primary annealed or coarsegrained fully lamellar) was examined both by mechanical-loss (internal-friction) and creep experiments. The mechanical-loss spectra (0.01– 10 Hz), ranging from 300 up to 1300 K, show two phenomena: (i) A loss peak at about 900 K (0.01 Hz) which occurs only in samples with a lamellar microstructure. The activation enthalpy, determined from the frequency shift, is 3.0 eV. The Debye-type peak is related to thermally activated reversible local movement of dislocation segments which are pinned at the lamellae interfaces and within gamma lamellae, (ii) A high-temperature damping background above 1000 K which is controlled by an activation enthalpy of 3.8 to 3.9 eV. This value agrees well with the activation enthalpy determined by creep tests and is in the range of values reported for self-diffusion of Al. These results indicate that both properties (high-temperature background and creep) are controlled by volume diffusion-assisted climb of dislocations.

On the vacancy nature of the high-temperature background of internal friction in solids

High-temperature internal friction in an amorphous CuTi alloy is investigated. Exponential regions with different activation energies are observed on the dependence of internal friction on temperature on both sides of the glass transition temperature. An exponential increase in the background of internal friction with temperature in both sites is associated with the migration of vacancy-like defects in the amorphous structure under the influence of mechanical stresses, while frozen defects of constant concentration migrate to the glass transition temperature. After the transition to a state of thermodynamic equilibrium, the concentration the number of migrating defects increases exponentially. Based on the experimental results of measuring the high-temperature background, estimates of the activation energy of migration and the formation of vacancies of similar defects in the amorphous structure of the alloy under study are made. Keywords: Internal friction, relaxation time, high temperature background, amorphous alloy.

Активационные характеристики вязкоупругих свойств жаропрочного сплава на основе системы Ni-Co-Cr, упрочненного объемным азотированием

The results of measurements of the high-temperature internal friction background of the heat-resistant alloy VZh171 in the initial state and after volume nitriding presented. The obtained data used to study the regularities of the transition from the elastic to the viscoelastic state of the material at elevated temperatures. Nitriding the alloy leads to an increase in the transition temperature to the viscoelastic state from 571 K (initial state) to 763 K (after nitriding). The values of activation energy of the high-temperature internal friction background obtained: U f = 0.63 ± 0.01 eV for the alloy VZh171 in the initial state and U f = 0.59 ± 0.01 eV for the alloy after volume nitriding. The activation energies U 0 of the processes responsible for the formation of the viscoelastic properties of the substance are estimated: U 0 ≈ 2.52 eV for the alloy in the initial state, U 0 ≈ 2.36 eV for the nitrided alloy. The obtained values U 0 correspond to the self-diffusion activation energy in nickel, the main component of the alloy matrix. The appearance of dispersed nitride phases in the matrix leads to a decrease in the activation energy of viscoelasticity processes by about 6%. Possible reasons for the change in the transition temperature and the activation energy of the viscoelastic state at moderately high temperatures as a result of nitriding discussed.

О вакансионной природе высокотемпературного фона внутреннего трения в твердых телах

High-temperature internal friction in an amorphous CuTi alloy is investigated. Exponential regions with different activation energies are observed on the dependence of internal friction on temperature on both sides of the glass transition temperature. An exponential increase in the background of internal friction with temperature in both sites is associated with the migration of vacancy-like defects in the amorphous structure under the influence of mechanical stresses, while frozen defects of constant concentration migrate to the glass transition temperature. After the transition to a state of thermodynamic equilibrium , the concentration the number of migrating defects increases exponentially. Based on the experimental results of measuring the high-temperature background, estimates of the activation energy of migration and the formation of vacancies of similar defects in the amorphous structure of the alloy under study are made.

Dynamic modulus, internal friction, and transient creep at high temperature in austenitic stainless steel

Dynamic shear modulus and internal friction of a coarse-grained austenitic stainless-steel sample (AISI 304) were measured by mechanical spectroscopy technique at elevated temperatures to 1200 ℃ and oscillation periods ranging from 1 s to 1000 s. The results were fitted to an extended Burgers model, showing a new thermally activated dissipation peak with relaxation strength 0.075 ± 0.005 superimposed on the high-temperature background. Across the temperature interval 1000–750 ℃, the dissipation peak traverses the 1–1000 s observational window with an activation energy of 210 ± 14 kJ/mol. Complementary time-domain information acquired by microcreep testing within the same temperature range reveals the extent to which the inelastic strain is recoverable (i.e. anelastic). A transient creep map was constructed to quantitatively analyze the contribution of different deformation mechanisms. The combined analysis involving Burgers model and a transient creep map highlights the likely role of stress-induced migration of dislocations in both the anelastic relaxation and the viscous deformation. This study thus provides a more robust understanding of the mechanical behavior of austenitic stainless steel at high temperatures and low strain amplitudes with implications, for example, for its use in jacketing other materials for mechanical testing under conditions of high temperature and pressure.

Notes on a compressible extended Burgers model of rheology

SUMMARY Constitutive theory for viscoelasticity has broad application to solid mantle or ice deformations driven by tides, surface mass variations, and post-seismic flow. Geophysical models using higher order viscoelasticity can better accommodate geodetic observations than lower-order theory, typically provided by tensor versions of Maxwell, 4-parameter Burgers or standard linear (Zener) rheology. We derive, for the first time, a mathematical description of a compressible version of the extended Burgers material (EBM) model paradigm which has a distribution function of relaxation spectra. The latter model is often used for parametrizing high temperature background transient responses in the rock physics and mechanics laboratory setting and have demonstrated application to low frequency seismic wave attenuation. A new generalization of this practical anelastic model is presented and applied to the glacial isostatic adjustment momentum equations, thus providing useful guidance for generating initial-value boundary problem-solving software for quite general coding strategies. The solutions for the vertical motion response to a suddenly imposed surface load reveal a short-term transience of substantial amplitude.

Grain boundary relaxation behavior and phase stability of AlCrTiVx (x = 0, 0.5 and 1) high-entropy alloys

The defect relaxation behavior of AlCrTiVx (x = 0, 0.5, and 1) high entropy alloys was reported in this paper. A pronounced internal friction (IF) peak superimposing on a monotonously increasing high-temperature background (HTBG) was observed in all samples, which was ascribed to grain boundary peak. The activation energy of grain boundary relaxation increases with the increasing V content, implying an increasing complexity and difficulty of atomic diffusion with the increasing mixing entropy. After annealing at 1100 °C for 5 h, the HTBG of AlCrTiV alloy abnormally increases, which was attributed to the appearance of misfit dislocations induced by precipitation of nano-sized Ti-rich phases as confirmed by microstructure analysis. These findings may provide a new degree of freedom for evaluating and designing high entropy alloys with high thermal stability.

The Relation between Trace Element Composition of Cu-(Fe) Sulfides and Hydrothermal Alteration in a Porphyry Copper Deposit: Insights from the Chuquicamata Underground Mine, Chile

Porphyry Cu-Mo deposits are among the world’s largest source of Cu, Mo, and Re, and are also an important source of other trace elements, such as Au and Ag. Despite the fact that chalcopyrite, bornite, and pyrite are the most common sulfides in this deposit type, their trace element content remains poorly constrained. In particular, little is known about minor and trace elements partitioning into Cu-(Fe) sulfides as a function of temperature and pH of the hydrothermal fluid. In this study, we report a comprehensive geochemical database of chalcopyrite, bornite, and pyrite in the super-giant Chuquicamata porphyry Cu-Mo deposit in northern Chile. The aim of our study, focused on the new Chuquicamata Underground mine, was to evaluate the trace element composition of each sulfide from the different hydrothermal alteration assemblages in the deposit. Our approach combines the electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of sulfide minerals obtained from six representative drill cores that crosscut the chloritic (propylitic), background potassic, intense potassic, and quartz-sericite (phyllic) alteration zones. Microanalytical results show that chalcopyrite, bornite, and pyrite contain several trace elements, and the concentration varies significantly between hydrothermal alteration assemblages. Chalcopyrite, for example, is a host of Se (≤22,000 ppm), Pb (≤83.00 ppm), Sn (≤68.20 ppm), Ag (≤45.1 ppm), Bi (≤25.9 ppm), and In (≤22.8 ppm). Higher concentrations of Se, In, Pb, and Sn in chalcopyrite are related to the high temperature background potassic alteration, whereas lower concentrations of these elements are associated with the lower temperature alteration types: quartz-sericite and chloritic. Bornite, on the other hand, is only observed in the intense and background potassic alteration zones and is a significant host of Ag (≤752 ppm) and Bi (≤2960 ppm). Higher concentrations of Ag and Sn in bornite are associated with the intense potassic alteration, whereas lower concentrations of those two elements are observed in the background potassic alteration. Among all of the sulfide minerals analyzed, pyrite is the most significant host of trace elements, with significant concentrations of Co (≤1530 ppm), Ni (≤960 ppm), Cu (≤9700 ppm), and Ag (≤450 ppm). Co, Ni, Ag, and Cu concentration in pyrite vary with alteration: higher Ag and Cu concentrations are related to the high temperature background potassic alteration. The highest Co contents are associated with lower temperature alteration types (e.g., chloritic). These data indicate that the trace element concentration of chalcopyrite, bornite, and pyrite changed as a function of hydrothermal alteration is controlled by several factors, including temperature, pH, fO2, fS2, and the presence of co-crystallizing phases. Overall, our results provide new information on how trace element partitioning into sulfides relates to the main hydrothermal and mineralization events controlling the elemental budget at Chuquicamata. In particular, our data show that elemental ratios in chalcopyrite (e.g., Se/In) and, most importantly, pyrite (e.g., Ag/Co and Co/Cu) bear the potential for vectoring towards porphyry mineralization and higher Cu resources.

Correlation between anelastic response and microstructure of 5N-Al thin foils

The anelastic behavior of 5N-Al thin foils with three different thicknesses (10, 50 and 125 µm) was investigated in the temperature range from 300 to 720 K through Mechanical Spectroscopy (MS) measurements performed by using a completely automated vibrating reed analyser. Two relaxation peaks P1 and P2 and a relevant high temperature background were observed in the thinnest samples whereas only the grain boundary peak (PGB) was observed in the thickest ones. Detailed TEM observations and X-ray diffraction (XRD) measurements indicate that defective structures depend on foil thickness and suggest that the origin of P1 and P2 peaks is connected to the vibration dynamics of isolated dislocations not organized in networks. P1 has been attributed to the combination of dislocatio n motion through the stress field of other dislocations and thermally activated cross slip, while P2 is due to the movement of jogs assisted by pipe diffusion. In addition to anelastic effects due to dislocation vibration, permanent grain boundary sliding seems to contribute to the high temperature background observed in the thinnest foils.

The effectiveness of the use of microbiological preparations when interacting with seed stocks of the genus Prunus L.

An important element of increasing the efficiency of production of high-quality planting material of fruit crops according to the criteria of environmental management, resource conservation and productivity is the use of adaptive, technological rootstocks, as well as microbiological preparations that are environmentally friendly and multifunctional. They stimulate plant growth by changing their hormonal status, act as fungicides, as bio protectors, forcing the plant turn into its defense mechanisms, as bio fertilizers that promote the absorption of atmospheric nitrogen by plants, hard-to-reach forms of phosphorus, a number of trace elements, have an anti-stress effect, etc. To control the process of obtaining seedlings of the highest quality category, it is necessary to study the living system “plant-microbiological preparation-environment”. As a result of this research, it was found that the high temperature background in combination with severe drought, observed during the years of research, adversely affected both the development of rootstocks in the first field of the nursery, and the effect of microbiological preparations. When developing resource-saving elements in technology - the selection of genotypes and microbiological preparations for growing rootstocks, bypassing the school of seedlings, form 3-106 was highlighted, when using the preparation Pseudobacterin-2. Found a regularity - a positive interaction in the conditions of the Ust-Labinsk district of OLL “Experimental Nursery (EN) named after K.A. Timiryazev” seedlings of rootstocks for sweet cherry and cherry, of different origin, and the preparation Pseudobacterin-2. In conditions of high temperatures in the spring-summer period, the isolated preparation increased the germination capacity and the yield of high-quality planting material.

Mechanisms of vibration damping in heat power engineering structural materials

This article explores two models of internal friction in porous materials and ultrafine-grain composite materials. The high-temperature background is described by two straight sections based on the dependence of the internal friction value on the reverse temperature or frequency of vibrations.

Multi-spectral temperature measurement based on adaptive emissivity model under high temperature background

When the object surface temperature in high temperature environment is measured by multi-spectral temperature measurement method, the radiation generated by the reflection of the high temperature background on the surface of the object and the radiation emitted by the object itself are both received by the pyrometer. For one thing, the amount of radiation received by the pyrometer increases. On the other hand, the surface emissivity model may change. So a large temperature measurement error may occur. In order to accurately measure the true surface temperature of an object in a high temperature environment, a multi-spectral temperature measurement method based on adaptive emissivity model is proposed in this paper. First, BP neural network is used to identify the shape of spectral data and obtain the correspondence between spectral data and emissivity model, then output the emissivity model that conforms to the measured target and specific environment. Moreover, the traditional NSGA-II algorithm (Non-dominant sorting genetic algorithm-II) is prone to falling into local optimal solutions and the numerical values obtained are not accurate enough. In this paper, the concepts of clustering algorithm, difference operator and symmetrical solution are introduced in the process of crossover and mutation, and then the new algorithm of INSGA-II (Improved Non-dominant sorting genetic algorithm-II)) is proposed. On the basis of this algorithm, the emissivity model of BP network is combined to solve the target true temperature. The experimental results show that the maximum temperature measurement error can reach 60 K if the influence of high temperature background is ignored. After removing the influence of high temperature background, the non-adaptive emissivity model was used to obtain the maximum temperature error of 30 K, and the fluctuation between adjacent temperature points was large. The multi-spectral temperature measurement method based on adaptive emissivity model proposed in this paper can obtain more accurate temperature measurement results with the maximum error of 8 K.