Search Results (29)

The Aptian–Albian interval represents a significant cooling phase within the Cretaceous “hothouse” climate, marked by dynamic climatic fluctuations. High-resolution continental records are essential for reconstructing terrestrial climate and ecosystem evolution during this period. This study examines a lacustrine-dominated succession of the Shahezi Formation (Lishu Rift Depression, Songliao Basin, NE Asia) to access paleo-weathering intensity and paleoclimate variability between the Middle Aptian and Early Albian (c. 118.2–112.3 Ma). Multiple geochemical proxies, including the Chemical Index of Alteration (CIA), were applied within a sequence stratigraphic framework covering four stages of lake evolution. Our results indicate that a hot and humid subtropical climate predominated in the Lishu paleo-lake, punctuated by transient cooling and drying events. Periods of lake expansion corresponded to episodes of intense chemical weathering, while two distinct intervals of aridity and cooling coincided with phases of a reduced lake level and fan delta progradation. To address the impact of potassium enrichment on CIA values, we introduced a rectangular coordinate system on A(Al₂O₃)-CN(CaO* + Na₂O)-K(K₂O) ternary diagrams, enabling more accurate weathering trends and CIA corrections (CIA_corr). Uncertainties in CIA correction were evaluated by integrating geochemical and petrographic evidence from deposits affected by hydrothermal fluids and external potassium addition. Importantly, our results show that metasomatic potassium addition cannot be reliably inferred solely from deviations in A-CN-K diagrams or the presence of authigenic illite and altered plagioclase. Calculations of “excess K₂O” and CIA_corr values should only be made when supported by robust geochemical and petrographic evidence for external potassium enrichment. This work advances lacustrine paleoclimate reconstruction methodology and highlights the need for careful interpretation of weathering proxies in complex sedimentary systems. Full article

In this study, the high-temperature thermal deformation behavior of the TA4 alloy was investigated by thermal compression experiments. The effects of deformation temperature and strain rate on the rheological stress are described by analyzing the variation of stress–strain curves with different parameters and establishing the constitutive equation based on the dynamic material theory model. Thermal processing diagrams were established and plotted to analyze the optimal processing zone and the destabilization zone under different strains. From the thermal machining diagram, it can be concluded that the optimum machining zone at a strain of 0.9 is 1040~1133 K/0.01~0.7 s⁻¹. The optimum machining zone at a strain of 0.6 is 940~1000 K/0.01~0.04 s⁻¹. The optimum machining zone at a strain of 0.3 is 940~1000 K/0.01~0.08 s⁻¹. The effects of different deformation conditions on the thermal deformation mechanism were analyzed in conjunction with EBSD characterization. The results showed that dynamic recrystallization (DRX) was the main deformation softening mechanism when at low strain rate (≤0.1 s⁻¹). At higher strain rates (>0.1 s⁻¹) and lower temperatures (<1083 K and ≥933 K), the main deformation softening mechanism was DRV; at higher temperatures (≥1083 K and ≤1133 K), the main deformation softening mechanism was DRX. Full article

Freeform carbon fibres were 3D-printed from CH₃OH:H₂O mixtures using hyperbaric-pressure laser chemical vapour deposition (HP-LCVD). The experiment overlapped a region of known diamond growth, with the objective of depositing diamond-like carbon without the use of plasmas or hot filaments. A high-pressure regime was investigated for the first time through the precursor’s critical point. Seventy-two C-fibres were grown from 13 different CH₃OH:H₂O mixtures at total pressures between 7.8 and 180 bar. Maximum steady-state axial growth rates of 14 µm/s were observed. Growth near the critical point was suppressed, ostensibly due to thermal diffusion and selective etching. In addition to nanostructured graphite, various carbon allotropes were synthesised at/within the outer surface of the fibres, including diamond-like carbon, graphite polyhedral crystal, and tubular graphite cones. Several allotropes were oversized compared to structures previously reported. Raman spectral pressure–temperature (P-T) maps and a pictorial P-T phase diagram were compiled over a broad range of process conditions. Trends in the Raman I_D/I_G and I_2D/I_G intensity ratios were observed and regions of optimal growth for specific allotropes were identified. It is intended that this work provide a basis for others in optimising the growth of specific carbon allotropes from methanol using HP-LCVD and similar CVD processes. Full article

In the present study, super austenitic stainless steel containing 7Mo-0.42N was isothermally treated at 1100 °C, 1200 °C, and 1250 °C for different times, in order to obtain the samples with different σ precipitate content of 7%, 1.4%, and 0.7%. The effect of σ phase content on the hot working properties of the specimens was investigated under hot compression conditions at 900~1200 °C and strain rates of 0.01~5 s⁻¹. Results show that, with the increase in σ content, the recrystallized grains increase gradually, and the internal stress decreases firstly and then increases. Therefore, the σ phase has two roles in the thermal deformation process. One is that the σ phase promotes recrystallization and the other is that the σ phase hinders dislocation motion. In the hot working diagram of super austenitic stainless steel with different σ phase contents, the distribution of high power consumption and instability regions is significantly different. The sample containing 1.4% σ phase does not show the region where the power dissipation coefficient η is negative, and there is a large number of dynamic recrystallized grains in the high power region, showing good hot working performance. However, the local rheology and cracking in samples containing 0.7% and 7% σ phase after deformation are more serious. Combined with the constitutive equation, hot working diagram, and microstructure, it is found that the optimum hot working property of the super austenitic stainless steel containing 7Mo-0.42N could be obtained when it is deformed at a temperature of 1200 °C with a strain rate of 5 s⁻¹ when the content of σ phase is 1.4%. Full article

Conventional lubricant testing methods focus on lab-scale constant contact conditions, which cannot represent the scenarios in actual hot-stamping processes. In recent studies, the concept of the ‘digital characteristics (DC)’ of metal forming has been proposed by unveiling the intrinsic nature of the specific forming, which presents a timely solution to address this challenge. In this work, the transient behaviours of three dedicated lubricants during the hot stamping of AA6111 material were investigated considering the effects of various contact conditions using an advanced friction testing system, and the interactive friction modelling was established accordingly. The lubricant limit diagram (LLD) of each lubricant was then generated to quantitatively evaluate the lubricant performance following the complex tool–workpiece interactions based on the tribological DCs, and a detailed investigation on the lubricant failure regions was conducted based on the interactive friction modelling. Finally, the industrial application index (IAI) was proposed and defined as a comprehensive evaluation of lubricant applications in the industry, and the most suitable lubricant was identified among the three candidates for mass production. Full article

For this article, hot compression tests were carried out on homogenized 2050 Al-Cu-Li alloys under different deformation temperatures and strain rates, and an Arrhenius-type constitutive model with strain compensation was established to accurately describe the alloy flow behavior. Furthermore, thermal processing maps were created and the deformation mechanisms in different working regions were revealed by microstructural characterization. The results showed that most of the deformed grains orientated toward <101>//CD (CD: compression direction) during the hot compression process, and, together with some dynamic recovery (DRV), dynamic recrystallization (DRX) occurred. The appearance of large-scale DRX grains at low temperatures rather than in high-temperature conditions is related to the particle-stimulated nucleation mechanism, due to the dynamic precipitation that occurs during the deformation process. The hot-working diagrams with a true strain of 0.8 indicated that the high strain-rate regions C (300 °C–400 °C, 0.1–1 s⁻¹) and D (440 °C–500 °C, 0.1–1 s⁻¹) are unfavorable for the processing of 2050 Al-Li alloys, owing to the flow instability caused by local deformation banding, microcracks, and micro-voids. The optimum processing region was considered to be 430 °C–500 °C and 0.1 s⁻¹–0.001 s⁻¹, with a dissipation efficiency of more than 30%, dominated by DRV and DRX; the DRX mechanisms are DDRX and CDRX. Full article

The hot compression simulation testing machine was utilized to conduct compression experiments on an Al-Mg-Si-Mn alloy containing the rare earth element Sc at a deformation temperature ranging from 450 to 550 °C and a strain rate of 0.01 to 10 s⁻¹. The study focused on the hot deformation behavior of the aluminum alloy, resulting in the determination of the optimal range of deformation process parameters for the alloy. The relationship between material flow stress, deformation temperature, and strain rate was described using the Arrhenius relationship containing thermal activation energy based on the stress-strain curve of hot compression deformation of aluminum alloy. This led to calculations for structural factor A, stress index n, and stress level parameters as well as thermal deformation activation energy to establish a constitutive Formula for hot deformation rheological stress of aluminum alloy and calculate the power dissipation factor η. Through this process, an optimized range for the optimal deformation process parameter for aluminum alloy was determined (deformation temperature: 490~510 °C; strain rate: 0.05 s⁻¹) and verified in combination with mechanical properties and microstructure through hot extrusion deformation trial production. Full article

Thermal deformation behavior of Cu–Cr–Sn alloy ingots under deformation temperatures ranging from 600 °C to 950 °C and strain rates from 0.01 s⁻¹ to 10 s⁻¹ was investigated in detail. The thermal deformation constitutive equation and thermal processing map of the alloy were established, respectively. The activation energy Q was determined as 430.61 KJ/mol. The optimal deformation system corresponding to the hot working diagram was a deformation temperature of 900 °C and strain rate of 0.1 s⁻¹. Under these deformation conditions, twin dynamic recrystallization (TDRX), continuous dynamic recrystallization (CDRX), and discontinuous dynamic recrystallization (DDRX) occurred simultaneously, with the twinning process causing the stress–strain curve to exhibit a wavy change. The thermal deformation microstructure of the alloy is co-regulated by different recrystallization mechanisms, with DDRX occurring mainly at low deformation temperatures, and both CDRX and DDRX occurring at high deformation temperatures. Full article

Fe₄₀Mn₂₀Cr₂₀Ni₂₀ medium-entropy alloy (MEA) has a single-phase crystal structure with high strength and good ductility at room temperature. It is important to study the hot deformation behavior for this alloy at a partially recrystallized state for possible high-temperature applications. In this investigation, the tensile tests were conducted on sheet materials treated via cold rolling combined with annealing at strain rates of 1 × 10⁻³–1 × 10⁻¹ s⁻¹ and deformation temperatures of 573–873 K. And the hyperbolic sine model was used to study the relationship between the peak stress, deformation energy storage and Zener–Hollomon parameter (Z parameter) of Fe₄₀Mn₂₀Cr₂₀Ni₂₀ medium-entropy alloys under high-temperature tension. According to the Arrhenius-type model, the constitutive equation of the alloys based on the flow stress was constructed, and the deformation activation energy and material parameters under different strain conditions were obtained. Based on the power dissipation theory and the instability criterion of the dynamic material model, the power dissipation diagram and the instability diagram were constructed, and the hot working map with a strain of 0.1 was obtained. The results show that the hyperbolic sine relation between the peak stress and Zener–Hollomon parameters can be well satisfied, and the deformation activation energy Q is 242.51 KJ/mol. Finally, the excellent thermo-mechanical processing range is calculated based on the hot working map. The flow instability region is 620–700 K and the strain rate is 2 × 10⁻³–4 × 10⁻³ s⁻¹, as well as in the range of 787–873 K and 2 × 10⁻³–2.73 × 10⁻² s⁻¹. The optimum thermo-mechanical window is 850–873 K, $\dot{\mathsf{\epsilon }}$ = 1 × 10⁻³–2 × 10⁻³ s⁻¹. Full article

Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM^® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 °C/550–600 °C/600–650 ° C/650–700 °C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 °C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values. Full article

High-arsenic water limits the utilization and development of water resources in Tibet, and high-arsenic groundwater is one of the major sources of arsenic input to surface water in the area. In this work, the characteristics of groundwater and the source and formation of arsenic in a typical watershed in Tibet (the lower tributaries of the Angqu River) were investigated using systematic surveys, ionic ratios, Gibbs diagrams, in combination with isotopic and heat storage calculation methods. The studies show that the chemical composition of the water in the study area is mainly determined by the rock weathering of carbonate and silicate rocks. The average recharge elevation levels of hot spring water are 4874.1 m, 4058.1 m, and 4745.0 m, respectively. Deep hot water is the main source of arsenic in the spring water, and its arsenic flux accounts for 98.44–99.77% of the measured flux in the spring water. Full article

The hot compression experiment of homogenized Al−5.2Mg−0.6Mn−0.29Zn−0.16Er–0.12Zr alloy was carried out by the Gleeble-3500 thermal simulation testing system. The deformation behavior in temperatures of 350~500 ℃ and deformation rates of 0.01~10 s⁻¹ was studied. The relationship between stress and strain rate and deformation temperature was analyzed. The constitutive equation of alloy high-temperature deformation was constructed by the Zener–Hollomon method, and the hot working diagram with the true strain of 0.2 and 0.5 was constructed according to the dynamic material model. The research results show that flow stress has a positive correlation with strain rate and a negative correlation with temperature. The steady flow stress during deformation can be described by a hyperbolic sinusoidal constitutive equation. Adding Er and Zr into Al−Mg alloy can not only refine grains and strengthen precipitation but also form a core–shell Al₃(Er, Zr) phase. In the deformation process, Al₃(Er, Zr) precipitates can pin dislocations and inhibit dynamic recrystallization (DRX). Dynamic recovery (DRV) is dominant during hot deformation. The mechanism of dynamic recovery is dislocation motion. At high temperatures, Al₃(Er, Zr) can also inhibit grain coarsening. The average hot deformation activation energy of the alloy is 203.7 kJ/mol. This high activation energy can be due to the pinning effect of Er and Zr precipitates. The processing map of the alloy was analyzed and combined with the observation of microstructure, the hot deformation instability zone of the alloy was determined, and the suitable process parameters for hot deformation were obtained, which were 450~480 °C, and the strain rate is 0.01~0.09 s⁻¹. Full article

Co-crystal materials formed by stacking different molecules with weak interactions are a hot research topic. In this work, we theoretically investigate the intermolecular interactions and charge transfer properties of the supramolecular BDBT-TCNB co-crystal (BTC). The π-π bonds, hydrogen bonds, and S-N bonds in the BTC bind the BDBT and TCNB molecules together to form a highly ordered co-crystal and lead to the co-crystal’s excellent two-photon absorption (TPA) properties. The intermolecular interactions of the BTC are discussed in detail by the independent gradient model based on Hirshfeld partition (IGMH), atoms in molecules (AIM), electrostatic overlay diagram, and symmetry-adapted perturbation theory (SAPT) energy decomposition; it is found that there is a strong interaction force along the stacking direction. The charge transfer properties of the one-photon absorption (OPA) and TPA of the BTC were investigated by charge density difference (CDD) and transition density matrix (TDM). It is found that the dominant charge transfer mode is the cross-space charge transfer along the stacking direction. Therefore, strong intermolecular interactions will promote intermolecular cross-space charge transfer. This work is of great significance for the design of organic optoelectronic supramolecular materials. Full article

The study relates to the use of automated plant protection systems in agriculture. The article presents a proprietary automated mobile platform with an aerosol generator of hot mist. Furthermore, the cause of the loss of a chemical preparation in the spraying of plant protection products on the tree crown was determined in the course of field research. A statistical analysis of the results of experiment was carried out and the effect of droplet size on leaf coating density was determined. The manuscript presents a diagram of the degree of penetration of the working solution as it drops into the crown of the tree, as well as a cross-sectional graph of the permeability of the spray from the projection of the fruit tree crown. The most effective modes of operation of the automated mobile platform for spraying plant protection products with a mist generator aggregate were established. Analysis of the results shows that the device meets the spraying requirements of the procedure for spraying plant protection products. The novelty of this research lies in the optimal modes identified by movement of the developed automated mobile platform and the parameters of plant treatment with protective equipment when using a hot mist generator. The following mode parameters were established: the speed of the automated platform was 3.4 km/h, the distance to the crown of the tree was 1.34 m, and the flow rate of the working fluid was 44.1 L/h. Average fuel consumption was 2.5 L/h. Effective aerosol penetration reduced the amount of working fluid used by up to 50 times. Full article

High strength Al-Li alloy is the research focus of aluminum alloy. In the present paper, high strength Al-Li alloy 2A97 composed of Al-Li-Cu-Zn-Mg-Mn-Zr system is studied by thermodynamic and kinetic calculation. The equilibrium phase diagram and the metastable phases of 2A97 were calculated by thermodynamic method. The solidification phase diagram of 2A97 was obtained using the Scheil–Gulliver model. The continuous cooling transformation diagram and isothermal aging curves were calculated using the kinetic method. In addition, the 2A97 microstructures of cast, homogenized, hot-rolled, and solid solution were observed by a scanning electron microscope. The results can be used for the process optimization and microstructure control of 2A97. In particular, the research results of this work can be used for the determination of the homogenization temperature and solid-solution temperature. Full article