Recrystallization Conditions Research Articles

Neural Network Based Adaptation Algorithm for Online Prediction of Mechanical Properties of Steel

After production of a steel product in a steel plant, a sample of the product is tested in a laboratory for its mechanical properties like yield strength (YS), ultimate tensile strength (UTS) and percentage elongation. This paper describes a mathematical model based method which can predict the mechanical properties without testing. A neural network based adaptation algorithm was developed to reduce the prediction error. The uniqueness of this adaptation algorithm is that the model trains itself very fast when predicted and measured data are incorporated to the model. Based on the algorithm, an ASP.Net based intranet website has also been developed for calculation of the mechanical properties. In the starting Furnace Module webpage, austenite grain size is calculated using semi-empirical equations of austenite grain size during heating of slab in a reheating furnace. In the Mill Module webpage, different conditions of static, dynamic and metadynamic recrystallization are calculated. In this module, austenite grain size is calculated from the recrystallization conditions using corresponding recrystallization and grain growth equations. The last module is a cooling module. In this module, the phase transformation equations are used to predict the grain size of ferrite phase. In this module, structure-property correlation is used to predict the final mechanical properties. In the Training Module, the neural network based adapation algorithm trains the model and stores the weights and bias in a database for future predictions. Finally, the model was trained and validated with measured property data.

Hot deformation characteristics and dynamic recrystallization mechanisms of a Co–Ni-based superalloy

The hot deformation behavior of a Co–Ni-based superalloy was systematically investigated using thermal compression tests. Stress–strain curves showed a typical dynamic softening after peak stress, especially at high temperatures and low strain rates. An Arrhenius-type constitutive equation was developed to reveal the relationship between the flow stress, strain rate, and temperature, while a processing map was constructed based on the calculations from the stress-strain curves combined with microstructural observations to determine the optimum thermal deformation conditions. The extent of recrystallization was found to increase with increasing temperature, a decreasing strain rate, or an increasing strain. A complete dynamic recrystallization (DRX) condition was reached at 1050 °C/0.01 s−1/0.7. In addition, pre-existing annealing twins were replaced by discontinuous dynamic recrystallization (DDRX) grains along the twin boundaries and the twin-DRX (TDRX) grains in the twin interior. In the case of an un-twinned matrix, a combined DDRX and continuous DRX (CDRX) process occurred at high strain rates, in contrasted with a single DDRX process taking place at low strain rates.

Influence of niobium microalloying on the kinetics of static and dynamic recrystallization during hot rolling of medium-carbon high-strength steels

The temperature-strain conditions of dynamic and static recrystallization during hot deformation were determined at a rate of 1 sec–1 for medium-carbon steel microalloyed with titanium, boron, and vanadium containing different amounts of niobium. It was found that under hot rolling conditions niobium prevents the completion of dynamic recrystallization, and at temperatures below 970°C it drastically slows down static recrystallization in the pauses between successive reductions.

Is a High Photoluminescence Quantum Yield Good Enough for OLEDs? Can Luminescence Rigidochromism Be Manifest in the Solid State? an Optoelectronic Device Screening Case Study for Diphosphine/Pyrazolate Copper(I) Complexes

ABSTRACTThis paper provides a 4th manifestation of a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for critical discussion of contemporary literature in inorganic chemistry. (For the 1st, 2nd and 3rd manifestations, see: a) Otten, B. M.; Melancon, K. M.; Omary, M. A. “All That Glitters is Not Gold: A Computational Study of Covalent vs Metallophilic Bonding in Bimetallic Complexes of d10 Metal Centers – A Tribute to Al Cotton on the 10th Anniversary of His Passing,” Comments Inorg. Chem. 2018, 38, 1–35; b) Yaseen, W. K.; Sanders, S. F.; Almotawa, R. M.; Otten, B. M.; Bhat, S.; Alamo, D. C.; Marpu, S. B.; Golden, T. D.; Omary, M. A. “Are Metal Complexes “Organic”, “Inorganic”, “Organometallic”, or “Metal-Organic” Materials? A Case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates”, Comments Inorg. Chem. 2019, 39, 1–26; and c) Smith, J. B.; Otten, B. M.; Derry, P. J.; Browning, C.; Bodenstedt, K. W.; Sandridge, J. H.; Satumtira, N. T.; Zilaie, M.; Payne, J.; Nuti, R.; Omary, M. A.; Smucker, B. W. “Luminescent, Redox-Active (Dithiolato)Bis(Imine)Platinum(II) Divergent Complexes with Exchangeable Imine Ligands: An Experimental/Computational Study versus Their (Diimine)(Dithiolato)Platinum(II) Convergent Congeners”, Comments Inorg. Chem. 2019, 39, 188–215.) Herein, the dinuclear complexes {Cu[3,5-(CF3)2Pz](µ-dppm)}2 and {Cu[3,5-(CF3)2Pz](µ-dppm)}2•3THF were studied structurally, spectroscopically and via density functional theory (DFT). They were synthesized by reacting bis(diphenylphosphino)methane (dppm) with the cyclic trinuclear complex {μ-[3,5-(CF3)2Pz]Cu}3 to effect nuclearity reduction. Two forms of crystalline solids, {Cu[3,5-(CF3)2Pz](µ-dppm)}2 and {Cu[3,5-(CF3)2Pz](µ-dppm)}2•3THF have been obtained using different recrystallization conditions. The {Cu[3,5-(CF3)2Pz](µ-dppm)}2 complex was found through DFT computations to undergo a distortion from a Y-shaped coordination sphere in the S0 ground state toward a T-shape in the T1 photoexcited, lowest-lying, phosphorescent state. The distortion also causes the copper-copper bond length to contract and form an excimer bond (dCu-Cu = 2.577 Å). Experimentally, the presence of THF in the crystal was found to cause a blue shift, effecting a change in emission color from teal to blue to the naked eye, with a near-unity quantum yields (93%), rendering the latter solid suitable for inorganic LED applications but not OLEDs, as thin films exhibit a reduced quantum yield. Crystallographic evidence suggests that THF leads to a more compact lattice that makes the complexes more rigid and thus hinder the excited state distortions vs unsolvated crystals. Greater distortion leads to a lower energy radiative emission and thus a red shift in the emission color. Films were also studied and found to undergo further red shifting as a result of less rigidity in the media and more surface molecules susceptible to distortion, hence manifesting the luminescence rigidochromism optical phenomenon in the solid state as opposed to the traditional manifestation in frozen vs fluid solution. Photobleaching was studied in both the film and powder to assess photostability, which was superior in neat vs doped solids, which is also favorable for LED applications.

Convenient and Efficient Syntheses of Peptide Nucleic Acid Purine Monomers

Currently, peptide nucleic acids (PNAs) play an important role as therapeutic agents, molecular tools for diagnosis and detection of genetic diseases as well as in biosensor probes. This research aims to optimize the synthesis of aeg- and γ-(S)-Me PNA monomers based on L-Ala, intended for oligomerization according to the Boc protocol. The monomers were obtained through the condensation of the corresponding pseudopeptides with carboxymethyl purine nucleic bases. During the work, the optimization of benzyloxycarbonyl- N6-adenine-9-yl-acetic acid and benzyloxycarbonyl-N2-guanine-9-ylacetic acid was carried out. The synthesis of benzyloxycarbonyl-N6-adenine-9-yl-acetic acid was conducted in three stages based on adenine with an overall yield of 22%. At the same time, the conditions for effective recrystallization of the mixture after alkylation of benzyloxycarbonyl-N6-adenine with ethyl bromoacetic acid ether have been developed to isolate the desired N9-regioisomer. Also, the optimization of a known method for producing benzyloxycarbonyl-N2-guanine-9-ylacetic acid from 2-amino-6-chloropurine was carried out. The total yield of the five-stage scheme was 55%. Condensation of aeg- and γ-(S)-Me pseudopeptides with benzyloxycarbonyl-N6-adenine-9-yl-acetic acid and benzyloxycarbonyl-N2-guanine-9-yl-acetic acid was performed by the standard carbodiimide method, DCC/HOBt in DMF followed by the removal of C-terminal methyl protective group by alkaline hydrolysis. The structure of the new compounds obtained was confirmed by spectral analysis methods. This work provides simple and optimized methods for obtaining protected carboxymethyl purine bases and increasing the efficiency of the synthesis and synthesized purine PNA monomers in an acceptable yield.

Solubilities of 2,6‐Diamino‐3,5‐dinitropyrazine‐1‐oxide in the Binary Mixtures of DMSO+H2O, DMF+H2O and NMP+H2O in the Temperature Range from 293.15 to 323.15 K under the Atmospheric Pressure

AbstractRecrystallization is usually required for the application of 2,6‐Diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) as an energy material due to its poor crystal morphology. The study of its solubilities in binary solvent mixtures can provide primary support for optimizing the recrystallization and spheroidization conditions of LLM‐105. In the current work, the solubilities of LLM‐105 in the binary mixtures of dimethyl sulfoxide (DMSO)+H2O, N,N‐dimethyl‐formamide (DMF)+H2O and 1‐methyl‐2‐pyrrolidone (NMP) +H2O were measured by the gravimetric method in the temperature range from 293.15 K to 323.15 K under the atmospheric pressure. The results suggest that the solubility of LLM‐105 increases with the increase of temperature and the concentration of the solvent. The experimental data were then fitted with the modified Apelbalt equation, (CNIBS)/Redlich‐Kister equation and Jouyban‐Acree equation. All models fit the experimental data well, indicating that they can be used to predict the solubilities of LLM‐105 in the binary solvent mixtures. The thermodynamic parameters of the dissolution including enthalpy, standard entropy and Gibbs energy were calculated from the experimental data. It was found that the dissolutions of LLM‐105 in all test solvents were endothermic.

Determination of Critical Conditions for Dynamic Recrystallization of Commercially Pure Titanium

Abstract Microstructural evolution and mechanical properties are controlled by dynamic recrystallization (DRX) during industrial processing. To identify the critical condition for initiation of DRX, hot isothermal compression tests of commercially pure (CP)-70 titanium were conducted in a temperature range of 750°C–1,100°C and strain rate range of 0.001–10 s−1 to a true strain of 0.69. The critical condition for initiation of DRX can be identified from the inflection point on the strain-hardening rate (θ=∂σ/∂ε) versus flow stress (σ) curve. A third-order polynomial equation was fitted to the experimental θ−σ data to find out the inflection point. The results show that the critical stress (σc) for the initiation of DRX can be expressed as σc=−B/3A, where A and B are the coefficients of the third-order polynomial equation. It was observed that critical stress value depends on the deformation condition. The stress-strain curve was then normalized with respect to the peak stress (U=σ/σp vs.W=ε/εp), leading to a normalized value of critical stress, (Uc)=σc/σp=−B′/3A′, where A′ and B′ are the coefficients of the normalized third-order equation. The value of Uc(≈0.95) is a constant and independent of deformation conditions. These parameters were then used to calculate the DRX fraction, and the relationship between DRX fraction and processing variables was established.

Hot tensile deformation mechanism and constitutive equation of AZ61Ce magnesium alloy sheets

To explore the hot tensile deformation characteristics of aged and homogenized AZ61Ce magnesium alloy sheets, the constitutive equation, initial condition of dynamic recrystallization (DRX) and microstructure are investigated in terms of uniaxial hot tensile testing in a temperature range of 473–723 K and a strain rate range of 0.003–0.1 s−1. Dynamic strain aging (DSA) is easily caused under low temperature deformation conditions for the homogenized AZ61Ce sheet, while its counterpart aged AZ61Ce is not sensitive to DSA under these conditions. The constitutive equations for both the aged and homogenized AZ61Ce alloy sheets under peak stress are established by regression analysis of an Arrhenius-type hyperbolic sine function. The activation energy, Q, of the homogenized AZ61Ce alloy sheet is higher than that of the aged one because of the higher amount of solved Al atoms in the homogenized alloy matrix. The study of critical strain (εc) reveals that Mg17Al12 particles precipitated by aging promote the DRX nucleation and grain refinement during tensile deformation. In addition, the softening mechanism of the AZ61Ce alloy sheets at temperatures below 573 K is primarily dynamic recovery, while at temperatures above 573 K, it is DRX.

Agate mineralization in spilitized Permian volcanics from “Borówno” quarry (Lower Silesia, Poland) – microtextural, mineralogical, and geochemical constraints

Two forms of silica mineralization, i.e.: (1) vein agates and (2) moss agates, were encountered for the first time within spilitized (albite-rich) alkali-basalts from the upper parts of Borówno quarry (Intra-Sudetic Basin). Vein agates consist predominately of length-fast chalcedony evolving into strongly-zoned prismatic quartz with a distinctive blue cathodoluminescence. They exhibit the abundance of microtextures typical of epithermal vein systems (i.e. pseudo-bladed, flamboyant/feathery, jigsaw puzzle/mosaic, and Bambauer quartz), but also comprise numerous solid inclusions such as sulphides (pyrite, marcasite, chalcopyrite, and chalcocite), sulphates (barite), carbonates (calcite, dolomite), carbonaceous material, and hematite. The formation of vein agates was marked by strong variations in physicochemical conditions (pH, silica content) of SiO2-bearing fluids and recrystallization of metastable silica phases (i.e. moganite), coupled with the local replacement of pre-existing sulphates and/or carbonates by silica during boiling-related conditions. Their LREE-enriched rare-earth patterns with positive Eu anomaly invoke the close relationship between host rocks alterations (spilitization) and origin of SiO2-rich fluids. Conversely, moss agates have formed as a result of a spherical growth of siliceous phases within vesicles and contain numerous mineral inclusions of hematite, goethite, anatase, as well as ore-related phases (mottramite and dickite). The examination of their surface micro-morphology showed a strong age-related maturation marked by the development of stacked silica plates (plate-edge-like structure). The botryoidal-shaped, white-coloured, and Al-enriched outermost layer of these agates possibly reflects a rapid deposition of the initial silica gel onto the cavity walls. The HREE-enriched rare-earth patterns of the moss agates, combined with the presence of positive Eu and Ce anomalies, suggest their parental SiO2-rich fluids could be derived from multiple sources (e.g. volcanics mesostasis and/or meteoric waters). The fluids responsible for the formation of agate mineralization within alkali-basalts in Borówno could be derived from syn- or post- alterations of their host rocks.

Critical conditions and grain growth model for dynamic recrystallization of Cu-Ni-Si alloy

Hot compression tests of Cu-Ni-Si alloy with high Ni and Si contents were performed at the deformation temperatures of 750–950 °C, and the strain rates of 0.01–10 s−1 on a Gleeble-3800 thermo-mechanical simulator. The critical conditions for dynamic recrystallization (DRX) of Cu-Ni-Si alloy were obtained by processing the collected data and combining with the inflection point of θ-σ curve with the minimum value criterion of −∂θ/∂σ-σ curve. There was a certain correlation between the critical strain (εc) and the peak strain (εp), that was, εc/εp = 0.723, and the functional relationship between εc and Z parameter was εc = 1.05 × 10−3Z0.059. The average recrystallized grain size under various deformation conditions was measured, and the DRX grain growth model of Cu-Ni-Si alloy was established as dDRX = 5650.4ε̇−0.12891exp(−73142/RT).

Atomistic simulations of grain boundary migration under recrystallisation conditions

We present details of an approach to simulating the migration of grain boundaries using classical molecular dynamics (MD) in a regime in which the boundary motion is driven by the presence of dislocation defects resulting from plastic deformation. By simulating the shrinkage of spherical grains of deformed material embedded in a perfect crystal, we create conditions in which grain boundary motion takes place on time scales accessible to MD simulations, in which the defect free energy acts as a driving force additional to the capillary force due to excess grain boundary energy. This approach is particularly flexible in allowing arbitrary choices of misorientation axis and angle and providing an interface in which all grain boundary plane orientations are represented. This flexibility is at the cost of additional complexity in the system under study and we establish an approach suitable for analysing the excess grain boundary energy and the components of the force for boundary motion on a local basis over the surface of the shrinking grain. We demonstrate that this approach is able to resolve variation in the grain boundary energy related to the intrinsic grain boundary dislocation network in lower angle boundaries and to detect local maxima in the driving force due to the dislocation structure within the deformed grain. We show that the variation in measured grain boundary velocities is accounted for by the excess energy of the dislocations. We further show that the presence of dislocations in the shrinking grain has a tendency to reduce the anisotropy in grain boundary behaviour. Indicative evidence is presented that the dislocation network may act as a focal point for mechanisms of grain boundary migration.

Critical Conditions for Dynamic Recrystallization of Hot Deformed 1 wt% Chromium - 1 wt% Molybdenum Rotor Steel

A medium carbon 1 wt% Chromium and 1 wt% Molybdenum low-alloy steel is an important material for making of rotors of turbines. Its hot forging requires precise control of temperature, strain, and strain rate for defect-free forging. In a view of this, this steel was subjected to a hot compression test in a thermomechanical simulator, Gleeble 3800®. Hot compression was carried out at temperatures of 900°C, 1,000°C, and 1,100°C. At each temperature four strain rates, i.e., 0.001 s−1, 0.01 s−1, 0.1 s−1 and 1 s−1, were used. Constitutive equations were used to analyze hot flow behavior, material constants, and activation energy. A mathematical model developed by Poliak and Jonas has been used to determine critical condition parameters like critical stress (σc), critical strain (εc), peak stress (σp), and peak strain (εp). For dynamic recrystallization (DRX), the variation of strain hardening rate up to steady state stress (σss), steady state strain (εss), and volume fraction of DRX (XDRX), with the help of Avrami-type models, have been discussed. Zener Hollomon parameters (Z) explained in terms of strain rate and steady state that flow stress (σss) has been expressed. Microstructures at different hot deformation conditions have been reported and explained.

Microstructure and its subsequent evolution of Sn37Pb/Cu column interconnect obtained by friction plunge welding

To optimize the column planting process of copper column grid array (CuCGA) package, friction plunge welding was proposed to implement the solder/Cu column interconnect assisted without mold. On account of friction and extrusion action during feeding of Cu column, high homologous temperature and large strain, which conformed to the condition of dynamic recrystallization, were generated in the solder zones near interface. The irregular island-like, fragment-like recrystallization α-Pb phases and striped-like α-Pb phases in β-Sn matrix formed at different distances from the interface of Sn37Pb/Cu column, respectively. Meanwhile, a thin, wave-like Sn/Cu diffusion layer formed at the interface. This indicates that micro-join can also be achieved by friction welding method, and the column planting is changed into a solid-state welding from conventional soft soldering. After the subsequent reflow soldering, the diffusion layer transformed into scallop-like, most α-Pb phases in the solder regressed to disk-like, and the pull-out load of joint is not lower than that of traditional column planting method.

Optimization of softening heat treatment for the Pt950Ru jewelry alloy

Platinum is one of the most precious metals in the world: 15 times rarer than gold and it is widely used in jewellery for its characteristic of unicity, incorruptibility, and colour neutrality. The standard grade in the jewellery industry is Platinum 950‰. In fact, pure platinum jewels are easily scratched, due to the poor hardness linked with the high purity. Among all the commercial alloys available, the Pt-Ru system is the one characterized by the highest mechanical properties. Aim of this work is to find an ideal softening heat treatment, in term of operating time and temperature. The heat treatment must be able to satisfy two main needs: it must permit to complete recrystallization of the work piece, preparing the material for further severe deformation by restoring high ductility and an equiaxed grain distribution; and at the same time, the final average grain size must be fine, in order to avoid counter side aesthetic effects that occur when grain size go over the micrometric scale. Due to its rarity, in literature there are few information about the alloy under discussion. To find the optimal parameters, several samples had been heat treated at different times and temperatures. Then they had been analysed by optical microscopy and with micro hardness tests, providing microstructure images and hardness data. By using a combination of three different temperatures and three different times, significant differences were found between the various samples both in terms of mechanical properties and of grain size. The comparison of the collected data permit to better understand the behaviour of the alloy under recrystallization conditions. In the end, it was observed that the dynamics of recrystallization changes significantly with relative small changes of temperature and was found that the optimal treatment to obtain a fine recrystallized microstructure with the desired mechanical properties is at 1000°C for 15 minutes.

A green recycling process of the spent lead paste from discarded lead-acid battery by a hydrometallurgical process.

In this study, a green recycling process of discarded lead-acid battery paste, which could avoid both the smelting and electro-winning route has been developed. Leaching reagents containing sodium citrate, acetic acid and hydrogen peroxide were reacted with spent lead paste in aqueous media at the pH of 5-6. Lead paste was leached and formed into lead citrate precursor, which was recrystallized and separated from the solution. The optimal conditions for the leaching process at room temperature were found to be the: concentration of acetic acid solution of 0.92 mol L-1; concentration of sodium citrate solution of 0.478 mol L-1; initial mass ratio of solid spent lead paste to liquid (solid/liquid ratio) of 1/5 g/mL; and reaction time of 2 hours. The results showed that the desulphurization efficiency of lead paste was up to 99.9%. The optimal conditions for lead citrate re-crystallization from the leaching mixed solution were found to be the re-crystallization temperature of 55oC for 5 hours in a water bath. The lead citrate precursor synthesized from discarded lead-acid battery pastes was the chemical formula of Pb3(C6H5O7)2·3H2O with columnar shape in the length of 30-50 μm, which was easily separated from the leaching solution. The results of kilogram-scale experiments made progress easier for obtaining the ultrafine lead oxide product (PbO and Pb) from discarded lead-acid battery paste.

Thermal Deformation Behavior and Critical Conditions of Dynamic Recrystallization of QCr0.8 Alloy

In this paper, the flow stresses, the constitutive equation, processing map and the critical conditions of dynamic recrystallization (DRX) of the hot forged QCr0.8 alloy are studied by hot compressive test in the 750-900°C temperature and 0.01-10s-1 strain rate ranges using Gleeble-1500D thermo-mechanical simulator. The compression reduction of thermal compression deformation is 50%. The results show that the thermal deformation temperatures and strain rates have a significant effect on the high temperature deformation behavior of the alloy. The higher the temperature, the smaller the strain rate and the easier the DRX of the alloy is found.The peak stresses of the alloy decreases with the increase of temperature and increases with the increase of the strain rates.The flow stresses during hot deformation can be described by a hyperbolic sine function. The activation energy Q of the thermal compression deformation is determined to be 370.8KJ/mol. The constitutive equation and processing map of the alloy are established. Critical strains of DRX εc are studied by the inflection point characteristic of the lnθ-ε curve of the alloy and the corresponding minimum value of the ∂θ (∂θ)/∂ε-ε curve.

Effect of the equal channel angular pressing route on the microstructural and mechanical behavior of Al-5086 alloy

The present paper analyzes the effect of the equal channel angular pressing (ECAP) routes A and Bc on the recrystallization conditions and mechanical properties of Al-5086 alloy. The specimens were processed up to 10 passes at 150 °C in a die with 120° inner angle. The recrystallized grains developed after the tenth pass in the route A. By increasing the number of passes the grains became finer and after the tenth pass, the average grain size became finer than 2 µm. The tensile and hardness tests results showed that in all passes, the route Bc had a stronger effect on the simultaneous improvement of strength and ductility. The fracture surfaces analyses showed that the local ductile behavior improves as increasing the number of passes. The textures analyses showed that the dominant component was altered from (111) to (200) and (220) plane by increasing the number of passes through both routes. Also, the dislocation density increased by increasing the number of passes.

Development and evaluation of data transfer protocols in the fully coupled random cellular automata finite element model of dynamic recrystallization

Development and application of the hybrid fully coupled, random cellular automata finite element (RCAFE) approach to modelling dynamic recrystallization phenomenon, during a high temperature deformation is the overall goal of the paper. The finite element (FE) solver provides information on equivalent stress, equivalent strain, temperature fields as well as on geometry of deformed computational domain after each time step. These data are transferred to the developed random cellular automata (RCA) model, which is responsible for evaluation of corresponding microstructure morphology evolution and dislocation density changes under dynamic recrystallization (DRX) conditions. Finally, a set of data from the RCA part is send back to the FE solver and used as an input for the next time step. As a result, the fully coupled RCAFE model for simulation of a DRX progress is established. Crucial developments of the RCA model related to the space deformation and efficient neighbors selection are presented within the paper. However, particular attention is put on the development of efficient communication algorithms and methods for input/output data transfer between the FE and RCA modules. The communication protocols based on text files and sockets have different levels of complexity but both are based on the Abaqus VUMAT subroutine. Their capabilities and limitations are evaluated within the paper. Finally, an application of the proposed RCAFE method to simulation of a dynamic recrystallization progress at the level of single grains is presented and discussed to highlight capabilities of the model.

Rheological Properties of the EP742-ID Alloy in the Context of Integrated Computational Materials Science and Engineering: Part I. Results of Experimental Investigations

Rheological properties of the EP742-ID alloy are investigated during high-temperature compression tests of cylindrical samples with various ratios of homological initial sizes of diameter and height (d0/h0). It is shown by the results of tests in ranges of temperature t = 1000–1150°C and initial deformation rates e0= 3 × 10–2–3 × 10–4 s–1 that an increase in the compression flow tension manifests itself at all temperatures and deformation rates with an increase in ratio d0/h0 with the linear dependence on the magnitude of e0 and ratio d0/h0. The procedure of recalculating characteristics of the deformation resistance for the specified ratio of homological parameters is proposed. An increase in the compression flow tension is associated with an increase in the rigidity coefficient of the samples and their specific contact surfaces. The temperature dependence of the apparent activation energy of the plastic deformation (Qdef) of the alloy and its relation with the phase composition and running conditions of the dynamic recrystallization of the γ-solid solution are established. The magnitude of Qdef in temperature conditions of the development onset of the dynamic recrystallization of the γ-solid solution (1000–1050°C) is 959 kJ/mol for samples with d0/h0 = 0.75. The largest values of Qdef for the samples with d0/h0 = 0.75 equal to 1248 and 1790 kJ/mol are observed in a temperature region of the intense dissolution and coagulation of the grain-boundary γ′-phase (1050–1100°C). The value of Qdef for the samples with d0/h0 = 3.0 increases to 2277 kJ/mol in this temperature range. The apparent activation energy of the plastic deformation lowers to 869 kJ/mol in the temperature region of the γ-solid solution with grain-boundary primary and secondary carbides (1100–1150°C). The results of compression of alloy samples during single and repeated sequential loading with various durations of pauses between deformation actions are presented. It is shown that no metadynamic recrystallization occurs in the experimental conditions in the γ + γ′-region, while it runs slowly in the γ-region.

Preparation and characterization of ultrafine Fe-O compound/ammonium perchlorate nanocomposites via in-suit growth method

In this paper, the ultrafine Fe-O compound/ammonium perchlorate (AP) nanocomposites were prepared via in-suit growth method. The structure and morphology of the nanocomposites were characterized by infrared spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion X-ray spectrometer (EDS) and transmission electron microscopy (TEM) test. The results showed that the prepared Fe-O compound nanoparticles were amorphous state and deduced as 2L-ferrihydrite. The size of Fe-O compound/AP nanocomposites could be effectively controlled by changing the recrystallization condition. 2L-ferrihydrite nanoparticles was evenly dispersed in the nanocomposites proved by EDS and TEM analysis. Furthermore, the thermal decomposition of Fe-O compound/AP nanocomposites was analysized by TG-DSC method. The prepared 2L-ferrihydrite nanoparticles of the nanocomposites showed good catalytic effect on AP because of their decreasing the decomposition temperature and increasing the total heat release of AP.