Search Results (233)

The present study systematically investigated the hot deformation behavior of GH2787 superalloy within the temperature range of 1060–1120 °C and strain rates of 0.1–10 s⁻¹. An Arrhenius-type constitutive equation was developed that accurately predicts the flow behavior, and the calculated thermal deformation activation energy Q is 364,401.19 J/mol. The hot working map was constructed based on the dynamic material model, which identified two preferred processing regions with power dissipation efficiency exceeding 0.3, and no flow instability was observed across the entire parameter range. Microstructural analysis reveals that the extent of dynamic recrystallization significantly increases with rising temperature and strain rate. Discontinuous dynamic recrystallization (via grain boundary bulging nucleation) serves as the dominant recrystallization mechanism in GH2787 superalloy during hot deformation, while continuous dynamic recrystallization (via subgrain rotation and coalescence) acts as a synergistic auxiliary mechanism, jointly driving microstructural evolution. This study provides important theoretical foundations for optimizing the hot working processes of GH2787 superalloy. Full article

GH2132, an Ni–Cr–Fe-based superalloy for aero-engine components, exhibits hot workability that is highly sensitive to processing parameters. The hot deformation behavior of GH2132 alloy was investigated via isothermal compression (Gleeble-3500-GTC) over 850–1100 °C and 0.001–10 s⁻¹, combined with optical microscopy and EBSD characterization. A strain-compensated Arrhenius-type hyperbolic-sine model was established, achieving high predictive accuracy (R² = 0.9916; AARE = 3.86%) with an average activation energy Q = 446.2 kJ·mol⁻¹. Flow stress decreases with increasing temperature and increases with strain rate, while microstructural softening transitions from dynamic recovery to complete dynamic recrystallization at higher temperatures and lower strain rates. Three-dimensional power-dissipation and hot-processing maps (Dynamic Materials Model) delineate safe domains and instability regions, identifying an optimal window of 1000–1100 °C at 0.001–0.01 s⁻¹ and instability at 850–900 °C with 0.01–0.1 s⁻¹. These results provide guidance for selecting parameters for hot deformation behavior during thermomechanical processing of GH2132. Full article

How continental lithosphere stretches and ruptures is a fundamental question in Earth sciences; however, effective constraints on the physical conditions deep within the crust where deformation is concentrated remain elusive. This study offers new insights into this process through a detailed dissection of the Tan-Lu Fault Zone, one of the most extensive fault systems in East Asia. A critical controlling factor for crustal rheological properties is deformation temperature, a challenge we address by employing a thermometer based on the fractal dimension (D-value) of dynamically recrystallized quartz grain boundaries. Analyzing 62 mylonite samples from the Feidong segment, we reveal that left-lateral strike-slip shearing along this fault zone occurred under high temperatures (~450–700 °C). This conclusion is not only derived quantitatively from a quartz D-value thermometer but is also visually corroborated by classic high-temperature microstructures (e.g., extensive grain boundary migration), corresponding to conditions from the upper greenschist to amphibolite facies. Existing geochronological data constrain this high-temperature shearing event to the Early Cretaceous. Such elevated temperature conditions, combined with field and microstructural evidence indicating extension, provide quantitative confirmation that the fault zone operated within a transtensional tectonic regime during that period. Our findings offer a rigorously thermally constrained dynamic model for the deformation behavior of large continental faults during large-scale lithospheric thinning and craton destruction, providing a valuable framework for interpreting crustal rheology and continental dynamics. Full article

The hot deformation behavior of the duplex structured Mg-9Li-5Al-2Sn-1.5Y alloy is investigated via hot compression tests in the temperature range of 200–350 °C and strain rate range of 0.001–1 s⁻¹. The flow behavior of the Mg-9Li-5Al-2Sn-1.5Y alloy is defined by hyperbolic constitutive equation. The Zener–Hollomon parameter Z is used in the hyperbolic-sine-type equation to express the relationships between the peak stress, deformation temperature, and strain rate. Dynamic recovery and dynamic recrystallization are the main characteristics that affect deformation behaviors. The activation energy Q is calculated as 127.89 kJ/mol. Based on the dynamic materials model, the processing maps at strains of 0.6 and 0.8 are constructed, and the optimum processing parameters are determined as the temperature range of 320–350 °C and strain rate range of 0.001–0.007 s⁻¹. Full article

In this study, we investigated the hot deformation behavior and microstructural evolution of a novel high-magnesium-content (high-Mg) aluminum alloy, bridging the disciplines of material processing and physical metallurgy. Uniaxial hot compression tests were performed over the temperature range of 280~400 °C and strain rates of 0.001~10 s⁻¹ to investigate its hot deformation behavior. The flow stress curves were systematically analyzed, and a constitutive model was developed to describe the thermo-mechanical response of the alloy. Microstructural evolution was characterized using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results indicate that dynamic recovery serves as the dominant softening mechanism at lower deformation temperatures (≤320 °C). As the temperature increased to 400 °C, a significant rise in dynamic recrystallization was observed. Moreover, at 400 °C, higher strain rates led to the formation of abundant, network-like, mushroom-shaped dynamically recrystallized grains. Full article

The current study explores the applicability of a single constitutive equation, based on the Arrhenius hyperbolic sine model, to a wide range of chemical compositions and test conditions by using a unique approximation. To address this challenge, a mixed model is proposed, integrating a physical model with phenomenological expressions to capture the strain and strain rate hardening, forming temperature, dynamic recovery (DRV) and dynamic recrystallization (DRX). The investigation combines high-temperature mechanical testing with modeling in order to understand the hot deformation mechanisms. Hot torsion tests were conducted on ten different low-carbon steels with distinct microalloying additions to capture their responses under diverse initial austenite grain sizes, deformation temperatures and strain rate conditions (d₀ = 22–850 µm, T = 800–1200 °C and $\dot{\epsilon }$= 0.1–10 s⁻¹). The developed constitutive equation has resulted in a robust expression that effectively simulates the hot behavior of various alloys across a wide range of conditions. The application of an optimization tool has significantly reduced the need for adjustments across different alloys, temperatures and strain rates, showcasing its versatility and effectiveness in predicting the flow behavior in a variety of scenarios with excellent accuracy. Moreover, the model has been validated with experimental torsion data from the literature, enhancing the applicability of the developed expression to a broader spectrum of chemical compositions. Full article

The hot deformation discipline of typical 45CrNi steel under a strain rate ranging from 0.01 s⁻¹ to 1 s⁻¹ and deformation temperature between 850 °C and 1200 °C was investigated through isothermal hot compression tests. The activation energy involved in the high-temperature deformation process was determined to be 361.20 kJ·mol⁻¹, and a strain-compensated constitutive model, together with dynamic recrystallization (DRX) kinetic models, was successfully established based on the Arrhenius theory. An improved second-phase (SP) cellular automaton (CA) model considering the influence of the pinning effect induced by SP particles on the DRX process was developed, and the established SP-CA model was further utilized to predict the evolution behavior of parent austenite grain in regard to the studied 45CrNi steel. Results show that the average absolute relative error (AARE) associated with the austenite grain size and the DRX volume fraction achieved through the simulation and experiment was overall below 5%, indicating good agreement between the simulation and experiment. The pinning force intensity could be controlled by regulating the size and volume fraction of SP particles involved in the established SP-CA model, and the DRX behavior and the average grain size of the studied 45CrNi steel treated by high-temperature compression could also be predicted. The established SP-CA model exhibits significant potential for universality and is expected to provide a powerful simulation tool and theoretical foundation for gaining deeper insights into the microstructural evolution of metals or alloys during high-temperature deformation. Full article

The effect of dislocation pile-ups responsible for the generation or annihilation of dislocations during friction of Ag and Ni was considered. The steady-state friction was accompanied by the formation of twin bundles, intersecting twins, dislocations, adiabatic elongated shear bands, and intense dynamic recrystallization. The mechanisms of microstructural stability and friction instability were analyzed. The theoretical models of dislocation generation and annihilation in nanocrystalline FCC metals in the context of plastic deformation and failure development under friction were proposed. The transition to unstable friction was estimated. The damage of Ag was exhibited in the formation of pores, reducing the contact area and significantly increasing the shear stress. The brittle fracture of Ni represents a catastrophic failure associated with the formation of super-hard nickel oxide. Deformation resistance of the dislocation structures in the mesoscale and macroscale was compared. The coefficient of similitude (K) has been introduced in this work to compare plastic deformation at different scales. The model of the strength–ductility trade-off and microstructural instability is considered. The interaction between the migration of dislocation pile-ups and the driving forces applied to the grain boundaries was estimated. Nanostructure stabilization through the addition of a polycrystalline element (solute) to the crystal interiors in order to reduce the free energy of grain boundary interfaces was investigated. The thermodynamic driving force and kinetic energy barrier involved in strengthening, brittleness, or annealing under plastic deformation and phase formation in alloys and composite materials were examined. Full article

The thermal deformation behaviour of a spray-formed 7055 as-forged aluminium alloy was studied using isothermal hot-press tests under different deformation conditions (strain rates of 0.01, 0.1, 1, and 10 s⁻¹, temperatures of 340, 370, 400, 430, and 460 °C). An Arrhenius constitutive model was developed using flow stress data corrected for friction and temperature, yielding a correlation coefficient (R) of 0.9877, an average absolute relative error (AARE) of 4.491%, and a deformation activation energy (Q) of 117.853 kJ/mol. Processing maps integrating instability criteria and power dissipation efficiency identified appropriate processing parameters at 400–460 °C/0.08–0.37 s⁻¹. Furthermore, this study investigated how strain rate and temperature influence microstructural evolution. Microstructural characterization revealed that both dynamic recovery (DRV) and dynamic recrystallization (DRX) occur simultaneously during thermal deformation. At low temperatures (≤400 °C), DRV and continuous dynamic recrystallization (CDRX) dominated; at 430 °C, deformation microstructures and recrystallized grains coexisted, whereas abnormal grain growth prevailed at 460 °C. The prevailing mechanism of dynamic softening was influenced by the applied strain rate. At lower strain rates (≤0.1 s⁻¹), discontinuous dynamic recrystallization (DDRX) was the primary mechanism, whereas CDRX became dominant at higher strain rates (≥1 s⁻¹), and dislocation density gradients developed within adiabatic shear bands at 10 s⁻¹. Full article

To address the coarse and mixed grain phenomena in ultra-large martensitic stainless steel forgings, this study investigated the hot deformation behavior of 04Cr13Ni5Mo martensitic stainless steel under deformation conditions of 950–1200 °C and strain rates of 0.001–0.1 s⁻¹ using Gleeble-1500D thermomechanical simulation tests. Based on the experimental data, the flow stress curves of the steel were obtained, and a dynamic recrystallization (DRX) kinetic model was established. The model was then integrated into finite element software for simulation to verify its reliability, providing theoretical guidance for optimizing high-temperature forging processes. The results demonstrate that dynamic recrystallization in 04Cr13Ni5Mo steel occurs more readily at temperatures above 1050 °C and strain rates below 0.1 s⁻¹. Under the selected hot compression test condition (1100 °C/0.01 s⁻¹), the simulated grain size in the central deformation zone was 48.98 μm, closely matching the experimentally measured value of 48.18 μm. This agreement confirms the reliability of finite element-based prediction and control of grain size in martensitic stainless steel forgings. Full article

Due to the frequent occurrence of coarse-grained structures in large hydrogenation tube sheets, their hydrogen resistance and corrosion resistance deteriorate, significantly shortening their service life. Therefore, microstructure evolution must be strictly controlled during the forging process. High-temperature compression tests were simulated using a Gleeble-1500D thermal simulator to investigate the hot deformation behavior of 14Cr1Mo pressure vessel steel under deformation conditions of 1050–1250 °C and strain rates of 0.01–1 s⁻¹. Based on the experimental data, the flow stress curve of 14Cr1Mo steel was obtained, and its thermal deformation behavior was analyzed. Furthermore, the dynamic recrystallization (DRX) kinetic model and grain size model of 14Cr1Mo steel were established. These models were then integrated into the finite element software Forge^® to validate the accuracy of the DRX models. The results showed excellent agreement between the simulated and experimentally measured grain sizes, with a maximum deviation of less than 8%, confirming the high accuracy of the dynamic recrystallization models. These models provide a theoretical basis for finite element simulation and microstructure control in the manufacturing of super-large pressure vessel tube sheet forgings. Full article

The effect of the temperature and strain rate during the hot rolling process on the microstructural evolution in fine-grained Ni₃Al intermetallic alloy doped with Zr and B was examined in this work. The hot rolling process was carried out at an initial temperature range of 1000, 1100, and 1280 °C and at a strain rate between 3.9 × 10⁻¹ s⁻¹ and 2.5 s⁻¹. The results of the EBSD microstructural analyses revealed that dynamic recrystallization phenomena are initiated at the rolling temperature of 1100 °C, while a fraction of the dynamically recrystallized grains further increases with both the rising temperature and strain rate of the deformation process. Furthermore, to estimate the heat losses during the hot rolling processing, a non-stationary heat transfer model was formulated and then used to evaluate the experimentally received data. Full article

In this study, we investigated the formation mechanism of organo-metal halide perovskite nanostructures through a two-step process categorized as dissolution–recrystallization. It is proposed that the initial formation of nanostructures is governed by the generation of seed grains, whereas the Ostwald ripening model explains only the subsequent growth stage of these structures. We suggest that newly generated grains—formed adjacent to pre-positioned grains—experience compressive stress arising from volume expansion during the phase transition from PbI₂ to the MAPbI₃ perovskite phase. Owing to their unstable state, these grains may serve as effective seeds for the nucleation and growth of nanostructures. Depending on the dipping time, diverse morphologies such as nanorods, plates, and cuboids were observed. The morphology, including the aspect ratio and growth direction of these nanostructures, appears to be strongly influenced by the residual compressive stress within the seed grains. These findings suggest that the shape and aspect ratio of perovskite nanostructures can be tailored by carefully regulating nucleation, dissolution, and growth dynamics during the two-step process. Full article

The rapid isolation of target constituents from natural products poses a significant challenge and is a key focus in current research. The Hosta plantaginea flower (HPF), a traditional Chinese medicinal herb, is primarily used to treat inflammatory diseases, with kaempferol as one of its major bioactive constituents. In this study, macroporous adsorption resin was used to purify total flavonoids (TF) from the HPFs. The 50% ethanol–water elution fraction of the TF was then recrystallized to yield kaempferol with a purity of 99.44%. Network pharmacology analysis identified 61 potential kaempferol-inflammation targets, which were linked to the PI3K-Akt and TNF signaling pathways. Molecular docking and molecular dynamics simulations revealed the stability and binding of kaempferol to PI3K, Akt, and TNF-α proteins. The analysis metrics included binding ability, the root mean square deviation (RMSD), radius of gyration, free energy landscape, solvent-accessible surface area, hydrogen bond count, RMS fluctuation, free binding energy, amino acid residue free energy decomposition, and principal component analysis. The anti-inflammatory mechanism of kaempferol was further validated in an LPS-induced RAW264.7 cell model, where it was shown to inhibit the PI3K-Akt and TNF-α signaling pathways. This study provides new insights into the anti-inflammatory mechanism of kaempferol and presents novel strategies for the rapid isolation of target constituents from natural products. Full article

Dynamic recrystallization (DRX) is a critical microstructural evolution mechanism in friction stir welding (FSW) of metallic materials, directly determining the mechanical properties and corrosion resistance of weld joints. In the field of DRX simulation, conventional models primarily consider intragranular dislocation strain energy as the driving force for recrystallization, while neglecting the elastic strain energy generated by coordinated deformation in polycrystalline materials. This study presents an improved DRX modeling framework that incorporates the multiphase-field method to systematically investigate the role of elastic strain energy in microstructural evolution during FSW of Al/Mg dissimilar materials. The results demonstrate that elastic strain energy can modulate nucleation and the growth of recrystallized grains during microstructural evolution, resulting in post-weld average grain size increases of 0.8% on the Al side and 2.1% on the Mg side in the FSW nugget zone. This research provides new insights into multi-energy coupling mechanisms in DRX simulation and offers theoretical guidance for process optimization in dissimilar material welding. Full article