Isothermal Annealing Research Articles

Influence of full-cycle heat treatment on microstructure and mechanical properties of CLF-1 steel

Based on the manufacturing requirements of tritium breeding blankets for fusion reactors, it is valuable to study the microstructure evolution and mechanical properties of CLF-1 steel, a candidate structural material, during the full-cycle heat treatment from profile to component. The full-cycle heat treatment includes isothermal annealing and multiple quenching and tempering treatments. Results indicate that multiple quenching and tempering treatments refine the size of prior austenite grains and reduce dislocation density and the width of lath martensite. With the increase in the number of quenching and tempering treatments, the CLF-1 steels exhibit a slight decrease in tensile strength while the impact toughness noticeably improves. Research has found that the effect of isothermal annealing treatment includes an increase in the size of the prior austenite grains and precipitates, as well as a change in the matrix from martensite to ferrite. As a result, the tensile strength and impact energy decrease sharply, while the ductility improves after isothermal annealing treatment. Subsequent quenching and tempering treatment can recover the microstructure and mechanical properties.

Crystallization of CoWB ternary boride in nickel-based metallic glass

The crystallization kinetics of CoWB ternary boride were investigated through non-isothermal differential scanning calorimetry experiments, using a Ni-based metallic glass precursor as the starting material. The effects of isothermal heat treatment temperature on the phase evolutions were also systematically studied. The results showed that the melt crystallization and glass crystallization behaviors of the alloy differ from each other. The continuous heating transformation diagram plotted from non-isothermal analyses is consistent with the results of isothermal heat treatments. A broad ternary boride precipitation zone was demonstrated, involving the gradual precipitation of CoWB crystals. Avrami exponent values for the early crystallization stage showed that the crystallization mechanism of CoWB is governed by the interface-controlled three-dimensional growth mechanism, and nucleation rate is high. As the crystallization progresses, a diffusion-controlled growth occurs and the nucleation rate decreases. This study offers insights into the heat treatment of CoWB-reinforced nickel matrix nanocomposites, benefiting future research and industrial production processes.

Isochronous and isothermal annealing of defects

The regularities of isothermal and isochronous discrete and continuous annealed material at a constant rate are considered on the example of monomolecular reaction and bimolecular recombination of Frenkel pairs. For isochronous annealing of radiation defects after neutron irradiation of GaP, process parameters were obtained.

Predicting the Global Distribution of Gryllus bimaculatus Under Climate Change: Implications for Biodiversity and Animal Feed Production

The potential range and distribution of insects are greatly impacted by climate change. This study evaluates the potential global shifts in the range of Gryllus bimaculatus (Orthoptera: Gryllidae) under several climate change scenarios. The Global Biodiversity Information Facility provided the location data for G. bimaculatus, which included nineteen bioclimatic layers (bio01–bio19), elevation data from the WorldClim database, and land cover data. For the near future (2021–2040) and far future (2081–2100) under low (SSP1-2.6) and high (SSP5-8.5) emission scenarios, the Beijing Climate Center Climate System Model (BCC-CSM2-MR) and the Institute Pierre-Simon Laplace Coupled Model Intercomparison Project (IPSL-CM6A-LR) were used. Assessing habitat gain, loss, and stability for G. bimaculatus under potential scenarios was part of the evaluation analysis. The results showed that the main environmental parameters affecting the distribution of G. bimaculatus were mean temperature of the driest quarter, mean diurnal temperature range, isothermality, and seasonal precipitation. Since birds, small mammals, and other insectivorous insects rely on G. bimaculatus and other cricket species as their primary food supply, habitat loss necessitates management attention to the effects on the food web. The spread of G. bimaculatus as a sentinel species in the food chain and its use in animal feeds are both impacted by habitat loss and gain.

Rapid detection of Puccinia striiformis f. sp. tritici from wheat stripe rust samples using recombinase polymerase amplification combined with multiple visualization methods

Puccinia striiformis f. sp. tritici (Pst), the airborne fungal pathogen of wheat stripe rust, causes a decline in wheat quality and severe yield loss. Effective field management of wheat stripe rust heavily relies on timely and accurate monitoring of incoming fungal sources. Therefore, rapid and accurate detection of Pst is invaluable in disease control programs. In this study, three assays using recombinase polymerase amplification (RPA) combined with different visualization methods, including RPA followed by agarose gel electrophoresis, RPA lateral-flow dipstick (RPA-LFD) technology, and real-time RPA, were developed for rapidly and sensitively detecting Pst. The RPA and RPA-LFD assays were conducted at an isothermal temperature of 39 °C within 30 min. The real-time RPA assay required only a 20-min reaction at 39 °C. The specificities of the three assays were determined based on the lack of cross-reactivity with the other seven control wheat pathogens. The detection limits of RPA and real-time RPA were 105 fg/μL, and that of RPA-LFD was 104 fg/μL. Additionally, the three RPA assays detected Pst in field leaf samples. Among the 73 samples examined, 44 (60.3 %), 45 (61.6 %), and 60 (82.2 %) tested positive in the RPA, real-time RPA, and RPA-LFD assays, respectively. The result suggested that RPA-LFD was the most sensitive in detecting Pst from field samples. Giving the simple, rapid, and practical nature of RPA assays, this method can serve as a promising molecular diagnostic tools for accurate and rapid detection of Pst.

Design and thermodynamic performance analysis of a novel adiabatic compressed air energy storage system based on liquid piston re-pressurization

Compressed air energy storage (CAES) is a crucial technology for integrating renewable energy into the grid and supporting the “dual carbon” goals. To further utilize compressed heat and reduce throttling losses, this paper proposes a novel A-CAES energy storage system with liquid piston re-pressurization (LP-A-CAES). During the energy release process, the air in the air storage tank enters the liquid piston directly without passing through the throttle valve, then undergoes further pressurization and expansion. This approach avoids throttling losses while increasing the expansion ratio of the expander, facilitating the efficient use of compressed heat. By establishing thermodynamic models for both the proposed re-pressurized A-CAES and the traditional A-CAES systems, we compare their performance variations with changes in key parameters. Results indicate that under design conditions, the system's energy efficiency is 70.74 %, a 5.07 % improvement over traditional throttle-based A-CAES systems. The total exergy loss of the system is 1.42 × 1010 J, with the compressor and expander units accounting for the largest exergy losses, at 32 % and 31.6 %, respectively. The liquid piston exhibits excellent isothermal performance, maintaining air and water temperature rises within 20 K and 2.5 K, respectively. Reducing the maximum pressure difference in the air storage tank enhances system performance, although the performance improvement of the re-pressurized A-CAES system compared to the traditional A-CAES system diminishes. Increasing the height of the thermal energy storage and reducing the diameter of the thermal storage material both contribute to higher system energy efficiency. When the height of the thermal energy storage increases from 4 m to 8 m, the system's efficiency rises from 70.04 % to 70.74 %. Similarly, reducing the diameter of the thermal storage material from 0.05 m to 0.01 m increases the system's efficiency from 68.85 % to 71.47 %.

Verification and Validation of the VANGARD Pinwise Nodal Code with Analyses of BEAVRS

This paper validates the graphical processing unit (GPU)–based pinwise nodal core calculation code VANGARD using the Benchmark for Evaluation And Validation of Reactor Simulations (BEAVRS), focusing on hot-zero-power (HZP) physics tests, hot-full-power (HFP) depletion, and load follow operation for both Cycles 1 and 2. Results are compared with measured data and other high-fidelity numerical solutions. In HZP physics tests, the critical boron concentration (CBC), control rod bank worth, and isothermal temperature coefficient agree well with measured data, satisfying the design review criteria for typical zero power physics tests. Pin power distributions for various rodded cases confirm the high accuracy of pin-resolved solutions compared to other numerical results. For HFP depletion, CBC closely matches measured data and other high-fidelity numerical solutions, showing differences smaller than 35 and 10 ppm, respectively, throughout the whole depletion steps. Computational performance analysis reveals that a cycle depletion of a realistic pressurized water reactor core can be completed within 3.5 min using a single gaming GPU, which affirms the feasibility of practical pinwise core designs.

Solubility and magnetic properties of Ag−Co−Si alloy synthesized by mechanical alloying and annealing

AbstractThis present work concerns the effect of ternary addition of non‐metallic and diamagnetic silicon on the metastable solubility of the immiscible silver‐cobalt system during the course of ball milling, annealing of the ball milled samples and the corresponding magnetic properties. It should be noted that silicon has a smaller goldsmidt radius (111 pm) than silver (144 pm) and silicon+4 has more valence electrons than silver+1. Keeping the objectives of the current study in mind, silicon may thus be considered as an option for ternary addition, in contrast to metallic components. An attempt has been made to examine the phase changes that occurred in the 50 silver‐40 cobalt‐10 silicon (atom percent) system during ball milling and the subsequent isothermal annealing of the ball milled product. Phase evolution during mechanical alloying and isothermal annealing is identified by means of x‐ray diffraction, differential thermal analysis, high resolution transmission electron microscopy and magnetic measurements. The addition of silicon facilitates cobalt‘s formation of a metastable alloy with copper after 50 hours of ball milling. Annealing significantly improves the magnetic characteristics of materials that have been ball milled; the optimal combination of magnetic properties was obtained after an hour of annealing at 550 °C.

Effects of Nb Solute and Precipitates on the Continuous Cooling and Isothermal Transformation of Pearlite in High‐Carbon Steel Wire Rods

To investigate the influence mechanism of Nb solute and precipitates on pearlite transformation, the effects of Nb content and heat‐treatment process on pearlite transformation and microstructure in high‐carbon steel wire rods are analyzed in this article. During the austenite deformation stage, the increase in solute Nb and strain‐induced precipitates (SIPs) suppresses austenite recrystallization, while the decrease in prior austenite grain size promotes the reduction of refined pearlite colonies size. During the continuous cooling transformation process, an increase in Nb content and cooling rate increases the supercooling of pearlite transformation and refines the interlamellar spacing (ILS) of pearlite. During the isothermal transformation process, the increase in isothermal temperature increases the incubation period of pearlite transformation and slows down the rate of pearlite transformation. With the increase in Nb content, the incubation period of pearlite transformation lengthens. But uneven distribution of C in austenite is caused by the SIP, which promotes interface migration, and shorts the pearlite transformation time. In high‐carbon steel wire rods, the refinement of pearlite colonies and pearlite ILS is achieved by increasing the Nb content, raising the cooling rate, and lowering the isothermal temperature, thereby increasing the content of precipitates and improving their mechanical properties.

Quantifying the Hydration‐Dependent Dynamics of Cu Migration and Activity in Zeolite Omega for the Partial Oxidation of Methane

AbstractCopper‐exchanged zeolite omega (Cu‐omega) is a potent material for the selective conversion of methane‐to‐methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu‐omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C. Applying a high‐temperature activation protocol at 450 °C causes a rapid deactivation of the material. This behavioral divergence is investigated by combining reactivity studies, neutron diffraction and in situ high‐resolution anomalous X‐ray powder diffraction (HR‐AXRPD), as well as electron paramagnetic resonance spectroscopy, to reveal that the migration of Cu throughout the framework is the primary cause of these behaviors, which in turn is predominantly governed by the degree of hydration of the system. This work suggests that control over the Cu migration throughout the zeolite framework may be harnessed to significantly increase the activity of Cu‐omega by generating more active sites for the MtM conversion. These results underscore the power of in situ HR‐AXRPD for unraveling the behavior of materials under reaction conditions and suggest that a re‐evaluation of Cu‐zeolites priorly deemed inactive for the MtM conversion across a broader range of conditions and looping protocols may be warranted.

Quantifying the Hydration-Dependent Dynamics of Cu Migration and Activity in Zeolite Omega for the Partial Oxidation of Methane.

Copper-exchanged zeolite omega (Cu-omega) is a potent material for the selective conversion of methane-to-methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu-omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C. Applying a high-temperature activation protocol at 450 °C causes a rapid deactivation of the material. This behavioral divergence is investigated by combining reactivity studies, neutron diffraction and in situ high-resolution anomalous X-ray powder diffraction (HR-AXRPD), as well as electron paramagnetic resonance spectroscopy, to reveal that the migration of Cu throughout the framework is the primary cause of these behaviors, which in turn is predominantly governed by the degree of hydration of the system. This work suggests that control over the Cu migration throughout the zeolite framework may be harnessed to significantly increase the activity of Cu-omega by generating more active sites for the MtM conversion. These results underscore the power of in situ HR-AXRPD for unraveling the behavior of materials under reaction conditions and suggest that a re-evaluation of Cu-zeolites priorly deemed inactive for the MtM conversion across a broader range of conditions and looping protocols may be warranted.

Microstructure and texture evolution of 2A12 aluminum alloy semi-solid billet prepared by SIMA process

In order to make up for the lack of research on the preparation process of semi-solid billet of 2A12 aluminum alloy, this paper adopts strain-induced melting activation (SIMA) process to prepare semi-solid billet of 2A12 aluminum alloy, and studies the effect of different SIMA process parameters on the microstructure and texture evolution. The results indicated a notable increase in both the average grain size (AGS) and shape factor (SF) with prolonged isothermal time under the condition of constant isothermal temperature. When the isothermal time is the same, the AGS is larger at low isothermal temperature, the SF is higher at high isothermal temperature, and the grain spheroidization is more obvious; The influence of the uneven strain distribution of the compression sample on the microstructure evolution during the subsequent semi-solid isothermal treatment (SSIT) process was studied by finite element method; At an isothermal temperature of 590°C and an isothermal time of 15 minutes, the recrystallization is basically completed, and the elongated grains are completely transformed into spherical isaemic crystals. The main texture types of the original extruded sample and the compression sample are <110> ‖CD and <010> ‖CD texture, respectively. The SSIT process will make the grain orientation approach to random orientation; The strong segregation of Cu and mild segregation of Mg and Zn were observed at the grain boundary during SSIT process; A suitable coarsening kinetic equation was determined, and the influence of isothermal temperature on the coarsening rate constant was studied.

Effect of isothermal annealing on yield anisotropy of AZ31 Mg alloy bars processed by ambient extrusion

Magnesium and its alloys show strong mechanical anisotropy due to their hexagonal close-packed structure. This paper processed ambient extrusion and subsequent annealing on AZ31 magnesium alloy bars to investigate the effect of working hardening and texture weakening on yield anisotropy of magnesium alloy. After ambient extrusion, yield strength on different loading direction are improved due to working hardening. ED-yield strength has the highest increment because work hardening has a higher effect on prismatic slip. Then, yield anisotropy becomes stronger with the increase of extrusion train. During annealing, static recrystallization occurs firstly in {101‾1} twinning zones and producing recrystallized grains with random orientation. With the growth of recrystallized grains, basal fiber texture is weakened gradually. Such weak basal texture can promote the activation of basal slip when loading along ED, so ED-yield strength shows a high decrement. On this way, the yield anisotropy in AZ31 magnesium alloy bars is weakened through ambient extrusion and subsequent annealing.

Development of colorimetric one-step reverse transcription loop-mediated isothermal amplification for rapid and visualized detection of tomato necrotic ringspot virus

Tomato necrotic ringspot virus (TNRV) stands out as one of the most destructive viruses affecting chili and tomato crops in Thailand. TNRV causes typical necrotic and chlorotic ringspot symptoms on both leaves and fruits. This study focused on the development of a colorimetric one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) for rapid and visualized virus detection in different host plants, including chili, tomato, and physalis, a weed found near tomato fields. The new set of LAMP primers was designed based on the sequence of the non-structural (NSs) protein and nucleocapsid (N) protein genes of TNRV. The assay was optimized to identify the optimum isothermal temperature and incubation period. Positive reactions were identified by a color change from pink to yellow, while negative reactions remained pink where the assay worked well at 65 °C for 30 min. Specificity and sensitivity assays were conducted. The results revealed that the optimal incubation time for detecting LAMP products, along with colorimetric changes, was 30 min at 65 °C. The specificity assay demonstrated where LAMP primers did not cross-react with other orthotospoviruses like capsicum chlorosis virus (CaCV), melon yellow spot virus (MYSV) and watermelon silver mottle virus (WSMoV). The sensitivity assay indicated that RT-LAMP detected TNRV from RNA diluted up to 10−7 (1.0 fg/μL). Evaluation of the colorimetric one-step RT-LAMP assay on naturally infected tomato, chili, and physalis samples confirmed its successful detection of TNRV.

Desulfurization Behavior of Magnetite Pellets Reduced by Isothermal Pure Hydrogen

The desulfurization behavior of magnetite pellets reduced by pure hydrogen at isothermal temperature is studied, the mechanism of self‐oxidation desulfurization is put forward, and the thermodynamic theoretical calculation and experimental verification of this mechanism are carried out. The feasibility of the reaction between iron sulfide and Fe3O4 is analyzed by HSC Chemistry 6.0 software. Additionally, a thermal gravimetric analyzer is used to further study the thermal behavior of pellet material under Ar atmosphere from 400 to 1400 K. The results show that the removal of sulfur in the isothermal reduction process of pure hydrogen does not depend on hydrogen phase diffusion and reduction temperature. During the heating process, self‐oxidation desulfurization occurs in the system, and the self‐desulfurization reaction is more inclined to Fe3O4 + FexSy → FeS + SO2. Under the experimental conditions, the temperature range of self‐oxidation desulfurization under conventional thermal field and microwave field is 700–1100 and 370–1140 K, respectively, and the desulfurization rate is 92.9% and 95.8%, respectively. The key to improving desulfurization by microwave radiation is that iron sulfide has good wave‐absorbing characteristics.

Investigation of the Softening Resistance Behavior and Its Mechanism in Cu-Ni-Si Alloys with Discontinuous Precipitates.

In this study, isothermal annealing experiments were conducted on copper-nickel-silicon alloys containing continuous precipitates (CP) and discontinuous precipitates (DP) to investigate the effects of different types of precipitate phases on the microstructural evolution and softening temperature during annealing, as well as to analyze the differences in softening mechanisms. The experimental results revealed that the softening temperature of the CP alloy, subjected to 75% cold deformation, was 505 °C. In contrast, the DP alloy achieved softening temperatures of 575 °C and 515 °C after 75% and 97.5% cold deformation, respectively. This indicates that the DP alloy exhibits significantly superior softening resistance compared to the CP alloy, attributed to the distinct softening mechanisms of the two alloys. In the CP alloy, softening is primarily influenced by factors such as the coarsening of the precipitate phase, the occurrence of recrystallization, and the reduction in dislocation density. In the DP alloy, the balling phenomenon of the DP phase is more pronounced, and its unique microstructure exerts a stronger hindrance to dislocation and grain boundary motion. This hindrance effect reduces the extent of recrystallization and results in a smaller decrease in dislocation density. In summary, the DP alloy, due to its unique microstructure and softening mechanisms, demonstrates better softening resistance, providing higher durability and stability for high-temperature applications.

High-temperature furnace for in situ GISAXS studies

Abstract A high-temperature furnace was constructed to perform in situ Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) experiments at high temperatures for isothermal studies. The furnace consists of two interconnected chambers: (i) a main chamber housing the heating elements, where the sample is inserted during GISAXS measurements, and (ii) a pre-chamber where the sample is maintained near room temperature until the temperature in the main chamber reaches the pre-selected value. The two-chamber design allows a rapid increase of the sample temperature and avoids the sample overheating, conditions desirable for studies of the formation and growth of nanoparticles under isothermal annealing. In a practical application, the furnace was used to investigate the kinetics of the formation of NiSi2 silicide nanocrystals endotaxially grown in Si(001) wafers. This experiment allowed us to gain insights into the growth process and evaluate the performance of the furnace for in situ GISAXS studies. The high-temperature furnace provides a robust tool for studying the effect of annealing temperature on the kinetics of the growth of nanoparticles in thermally activated processes with special advantages in studies in which isothermal conditions are required.&amp;#xD;

Effects of cerium micro-alloying on microstructural evolution and dispersion strengthening in Al-Yb-Er-Zr alloy

This study investigates the impact of trace cerium (Ce) addition on the precipitation behavior of Al-0.03Yb-0.03Er-0.06Zr (at%) alloys, with a focus on the formation of eutectic phases and nanoscale dispersoids. Ce, known for its low solubility in Al, preferentially segregates at grain boundaries, leading to the formation of Ce-rich eutectic phases and significant grain refinement. Isochronal annealing experiments revealed a double-peak hardening pattern. The first peak, associated with Al3RE (RE= Yb, Er, Ce) precipitates, demonstrated minimal sensitivity to Ce addition. The second peak, related to core-shell L12-Al3(RE, Zr) precipitates, exhibited a notable increase in hardness in the Ce-added alloy. Isothermal annealing at 450 °C and 475 °C further demonstrated that Ce accelerates the annealing-hardening response and increases the number density of Al3(RE, Zr) dispersoids at elevated temperatures. This enhancement may be attributed to Ce serving as an effective inoculant element and significantly reducing the stacking fault energy, which facilitates easier nucleation of these particles.

Annealing effect of Ca3TaGa3Si2O14 catangasite crystals on their optical activity

The spectral dependences of transmission and absorption in the wavelength range of 200–2500 nm were measured for Ca3TaGa3Si2O14 crystals cut perpendicular to the optical axis in the initial state (without annealing) and after isothermal annealing in vacuum and in air. It was found that annealing in vacuum leads to a decrease, and annealing in air leads to an increase in the intensity of absorption bands. A spectrophotometric method for measuring and calculating the specific rotation angle ρ of the plane of polarization of light in gyrotropic crystals from the transmission coefficient spectra at different angles between the polarizer and the analyzer is considered. The transmission spectra were normalized in order to eliminate shifts in the spectra associated with measurement features. Spectral dependences of the values of ρ for all three samples, which are approximated by the extended Drude formula, are obtained; the influence of the annealing atmosphere on the values of the coefficients of this formula is established.

On the Origin of Enhanced Tempering Resistance of the Laser Additively Manufactured Hot Work Tool Steel in the As-Built Condition

Abstract In laser additive manufacturing (AM) of hot work tool steels, direct tempering (DT) of the tool from as-built (AB) condition without prior conventional austenitization and quenching results in enhanced tempering resistance. To date, intercellular retained austenite (RA) decomposition, leading to a shift in secondary hardening peak temperature, and finer martensite substructure are reported to be responsible for such a behavior. In this work, authors aimed at studying the strengthening contributions by performing isothermal tempering tests for long times (up to 40 hours) at elevated temperatures (up to 650 °C) on DT and quenched and tempered (QT) specimens. The thermal softening kinetics and the microstructural evolution were evaluated with the support of computational thermodynamics. The results suggest that the main contributor to enhanced temper resistance in DT condition is the larger fraction of thermally stable and extremely fine (~ 20 nm) secondary (tempering) V(C,N) compared with QT. This could be explained by the reduction of available V and C in austenitized and quenched martensite for a later secondary V(C,N) precipitation during tempering, because of equilibrium precipitation of relatively large (up to 500 nm) vanadium-rich carbonitrides during the austenitization process. A complementary effect of the substructure refinement (i.e., martensite block width) in rapidly solidified highly supersaturated martensite was also quantified in terms of Hall–Petch strengthening mechanism. The significant effect of secondary V(C,N) was successfully validated by assessing a laser AM processed vanadium-free hot work tool steel in QT and DT condition, where no significant differences in strength and temper resistance between the two conditions were evident. Graphical Abstract