Isothermal Tests Research Articles

Systematic investigation of the microstructure evolution and dynamic recrystallization mechanisms of as-cast Fe–TiB2 composites under different hot deformation parameters

Fe–TiB2 composite shows great potential in lightweight materials for automotive parts due to its lightweight, high strength and high specific modulus etc. However, challenges remain with regard to establishing a fine hot working process of Fe–TiB2 composites. Here, a series of isothermal hot compression tests was conducted to systematically investigate the microstructure evolution and the dynamic recrystallization (DRX) mechanisms of as-cast Fe–TiB2 composites at different sets of hot deformation parameters. The results indicate the true stress drops more significantly after reaching its peak at low temperatures compared to high temperatures, since low temperatures favors the DRX through particle stimulated nucleation (PSN) in Fe–TiB2 composites, as featured by layers of DRXed grains surrounding TiB2 particles. Continuous dynamic recrystallization (CDRX) process gradually dominates as strain rate increase from 0.01 s−1 to 1 s−1 in Fe–TiB2 composites hot compressed to the true strain of 0.69 at 900 °C, as evidenced by the presence of DRXed grains with larger size and uniform distribution in matrix. DRX through PSN is the primary DRX mechanism at low temperature and low strain rate, while CDRX dominates the DRX mechanism at high temperature and high strain rate. Both DRX behaviors deepen with the increase of the strain. Different hot deformation parameters favor different DRX mechanisms. The increase in temperature and strain rate leads to a transition of the dominant recrystallization mechanism from the DRX through PSN to CDRX which is attributed to the competition for stored energy between the DRX through PSN and CDRX process.

A novel thermo‐mechanically coupled material model for glass above the glass transition temperature

AbstractThin glass products have a giant field of application in several engineering branches such as for example, electronics, medical equipment, and the automotive industry. The non‐isothermal glass molding is a novel replicative glass processing technology enabling the realization of a cost‐efficient production of surface shapes with high accuracy and complexity. However, the application of this technology to thin glass production still causes shape distortions, cracks, and surface defects in molded parts. Therefore, these glass‐forming processes should be simulated by means of the combination of experimental investigation and mechanical modeling of glass above the glass transition temperature at finite strains. Previous experimental studies have shown that the Maxwell model is a reasonable approach for an appropriate prediction of the material behavior. Based on this viscoelastic formulation, a thermo‐mechanically consistent material law is used enabling the prediction of rheological effects noticed during the experiments. More specifically, the relaxation behavior can be described by a stress‐dependent relaxation time and the dissipation generated is considered as well. Furthermore, isothermal uniaxial compression tests above the glass transition temperature are conducted for different strain rates and temperatures within the experimental investigation. Combining the experimental data with the simulation, a multi‐curve‐fitting leads to suitable material parameters with respect to distinct temperatures employing a nonlinear optimization.

Revealing microstructures evolution and dynamic recrystallization mechanisms of Mg–Sn–Mn alloy during compressive deformation at elevated temperature

The flow behavior of as-extruded Mg–3Sn-1.5Mn (wt.%) alloy was systematically researched via isothermal compression tests. The compressive temperatures (T) were from 250 °C to 400 °C, the strain rates were from 0.001 s−1 to 1s−1 and the true strain reached 0.69. Based on compression curves, flow stress apparently rose with increasing strain rate and/or decreasing temperature. Combined with the analysis of microstructure and processing map, the optimum working parameter was determined in the range of 350–400 °C, 0.01–1 s−1. According to electron backscatter diffraction (EBSD) analysis results, texture intensity significantly decreased and the basal (0001)//ED texture had transformed to basal <0001>//CD texture after compressive deformation obviously. Furthermore, the typical discontinue dynamic recrystallization (DDRX) and continue dynamic recrystallization (CDRX) were largely believed to be the major DRX mechanisms in Mg–3Sn-1.5Mn alloy. Both increasing temperature and decreasing strain rate had obvious influence on the degree of DRX. The activated slip systems in deformed grains were determined by the analysis of the in-grain misorientation axis (IGMA). As deformation temperature elevated, pyramidal <c+a> slip greatly activated and dominated compressive deformation.

Investigation of an optimized hot press process design for manufacturing structural polyethersulfone foams

Semi-finished thermoplastic foam panels can be transformed into structural foams—a sandwich-like structure with high-density skins—through thermoforming. This transformation enables the production of mono material sandwich panels, which allow a significant increase in bending properties without increasing the part weight. This study describes the effect of process parameters on skin formation in thermoplastic structural foams manufactured in a two-step isochoric and isothermal hot press process. Process data recorded during foam manufacturing was analyzed and compared to foam behavior in quasi-static isothermal compression tests performed at different levels of temperature and crosshead speeds. The effect of skin-core structure on bending properties is compared to theoretical models from the established literature. It was found that a rule of linear mixture that considers the relative skin thickness allows adequate prediction of both bending modulus and strength. Preferable process design—especially combinations of tool temperature and maximum compaction speed—is described based on the comparison of measured and predicted performance.

Influence of strain rates and aging time on microstructure and hardness of integrally compressed 6082 aluminum alloy

In this study, an in-depth analysis of the microstructure and hardness of 6082 aluminum alloy under a novel solution-forging integrated process was conducted by performing a series of isothermal uniaxial compression tests at various strain rates and aging durations. The results indicated that the highest hardness was 125.0 ± 1.2 HV at peak aging with a forming strain rate of 10 s−1; a 16.1% improvement compared to the conventional T6 forming process. The deformation reduced the subsequent peak aging time from 8 h in the conventional process to 6 h. In addition, the composite phases, including short-range disordered B'/U2 phase and composite phase with multiple structures, were also observed under a strain rate of 10 s−1 with 6 h of aging. As the strain rate increased, the grain size increased, accompanied by an increase in dislocation density. For the integrated process, the deformation microstructure would inherit to the aging state and affect the precipitation kinetics during aging, including grain morphology, dislocation density, and the aging precipitated phase, especially for the formation of composite phase; these were the main reasons for the higher hardness after ageing when compared to the hardness of the alloy under traditional T6 state.

Hot compressive deformation behavior of Ti-8Al-1Mo-1 V titanium alloy at elevated temperatures: Focus on flow behavior, constitutive modeling, and processing maps

The deformation behavior of the near-α Ti-8Al-1Mo-1 V titanium (Ti-811) alloy was studied by isothermal compression tests in the temperature range of 950–1075 °C and strain rates of 0.001–1 s−1. According to the physical properties of titanium alloys, the effects of adiabatic heat and friction during hot deformation process were modified on the stress-strain curves, especially at low temperatures and high strain rates. The results showed that the flow stress increases with increasing the strain rate and decreases with an increase in process temperature. Hyperbolic sine (sinh) and Cingara equations were used to model the flow behavior of Ti-811 alloy at elevated temperatures. Results showed a suitable fitting among the calculation and experimental results by the sinh equation at low strain rates (0.001 and 0.01 s−1) and by the Cingara equation at high strain rates (0.1 and 1 s−1). The activation energy values (Q) of Ti-811 alloy in two-phase and single-phase regions were calculated as 738 and 194 kJ/mol.K, respectively. The processing maps showed that in the single-phase region, the instability domain was located at 1025 °C and 1050 °C and high strain rates (0.1 and 1 s−1) and low strain rates (0.001 and 0.01 s−1) were considered as stability domain. For the α + β region, an instability domain was only observed at 1000 °C and 0.01 s−1. Microstructural observations showed occurring dynamic recrystallization, dynamic phase transformation, and globularization of alpha phase in stability domain.

Analysis of the High Temperature Plastic Deformation Characteristics of 18CrNi4A Steel and Establishment of a Modified Johnson–Cook Constitutive Model

To investigate the plastic deformation behavior of 18CrNi4A steel at high temperatures, an isothermal hot compression test was conducted on a Thermecmastor-Z series test machine at deformation temperatures from 1273 K to 1423 K and strain rates ranging from 0.01 s−1 to 10 s−1. The effects of these two factors on the flow stress were analyzed. Based on the true stress–strain experimental curves, the original Johnson–Cook constitutive model was applied to determine the flow stress data under different deformation conditions. The prediction results of the model were compared with the experimental data. The main reason for the large deviation observed between them was that the coupling relationship between the deformation temperature and the strain rate was not considered, so the original Johnson–Cook model was modified. The correlation coefficient and average absolute relative error of the original Johnson–Cook model were 0.962 and 16.36%. The prediction accuracy of the modified Johnson–Cook model was improved to 0.991 and 5.58%, respectively. The results show that the modified Johnson–Cook model exhibits higher prediction precision, which is beneficial for the broader application of 18CrNi4A steel in the industry.

Investigating the Static Recrystallization Behavior of 22MnB5 Manganese–Boron Steel through Stress Relaxation Analysis

A constitutive model was developed to characterize the static recrystallization (SRX) and evolution of the grain size of the industrially relevant press-hardening steel, 22MnB5, subsequent to the hot forming of sheet metal. Isothermal stress relaxation tests were conducted using the BAEHR 805 A/D thermomechanical simulator, encompassing a temperature range of 950 to 1050 °C, prestrain levels ranging from 0.01 to 0.1, and strain rates spanning from 0.01 to 0.8 s−1. The results obtained from the isothermal stress relaxation tests facilitated the formulation of an Avrami equation-based model, which aptly describes the kinetics of SRX in relation to the temperature, prestrain, and strain rate. Notably, an increase in temperature led to accelerated recrystallization kinetics, signifying temperature-dependent behavior. When the temperature increased from 950 to 1050 °C, the recrystallization time was reduced to approximately one-third. Additionally, the prestrain exhibited a positive influence on the acceleration of SRX kinetics. A quintupling of the prestrain from 0.01 to 0.05 resulted in a reduction of the static recrystallization duration to approximately one-fifth. Among the parameters studied, the strain rate had the least impact on the SRX kinetics, as doubling the strain rate from 0.01 to 0.8 only resulted in a halving of the recrystallization duration. Moreover, an analysis of the microstructural evolution in response to the forming parameters was undertaken. While the grain-size investigation post-isothermal stress relaxation tests provided results in line with the SRX kinetics calculations, the observed effects were comparatively subdued. Furthermore, a comprehensive examination was conducted using electron backscatter diffraction (EBSD) analysis, aiming to explore the effects of specific stress relaxation states on the morphology of martensite. The findings reveal fully recrystallized globulitic microstructures, characterized by relatively minor differences among them.

Semi-empirical degradation rate estimation of TiFe1-xMnx alloy for thermochemical hydrogen compression durability tests

The substitution effects of Fe by Mn in TiFe1-xMnx (x = 0.1–0.5) alloys on the cyclic durability for thermochemical hydrogen compressors were investigated. In the substitution ratio range of 0.1–0.5, TiFe1-xMnx alloy shows a single CsCl phase structure, and thus is further used for a thermochemical hydrogen compressor at 500 °C. The compression tests are performed for 26 cycles in temperature range from 25 °C to 500 °C. The variation of hydrogen storage capacity during pressure composition isotherm test and structural identification by x-ray diffraction measurements are conducted to investigate the cyclic durability of TiFe1-xMnx alloy at the above compression conditions. The Mn substitution increased the cyclic durability of TiFe for the thermochemical hydrogen compressor, and 30% of Mn (TiFe0.7Mn0.3) is the optimum ratio for the reduction rate of hydrogen storage capacity and achieved maximum pressure. In addition, TiFe0.5Mn0.5, as the respective sample with the maximum capacity loss, was evaluated by the acceleration test to estimate the lifetime of the alloys. The reaction kinetics v0 [(H/M)/s] of the capacity loss of TiFe0.5Mn0.5 is defined as ln v0 = 1.68 ln (PH2/P0) − (2.39 × 1000)/T − 18.967. Therefore, it is possible to predict the durability of TiFe1-xMnx alloy at different pressure and temperature conditions by the presented acceleration test.

Revealing the Influence of SiC Particle Size on the Hot Workability of SiCp/6013 Aluminum Matrix Composites.

SiC particle (SiCp) size has been found to significantly influence the hot workability of particle-reinforced aluminum matrix composites (AMC). In this work, therefore, three types of SiCp/6013 composites with different SiCp sizes (0.7, 5 and 15 μm) were prepared and then subjected to isothermal hot compression tests. In addition, constitutive analysis, processing maps and microstructural characterizations were used to reveal the influence of SiCp size on the hot workability of SiCp/6013 composite. The results showed that the values of hot deformation activation energy Q increased with decreasing SiCp size. Specifically, at lower temperatures (e.g., 350 and 400 °C), the highest peak stress was shown in the AMC with SiCp size of 0.7 μm (AMC-0.7), while in the AMC with SiCp size of 5 μm (AMC-5) at higher temperatures (e.g., 450 and 500 °C). This is because a finer SiCp size would lead to stronger dislocation pinning and grain refinement strengthening effects, and such effects would be weakened at higher temperatures. Further, dynamic softening mechanisms were found to transform from dynamic recovery to dynamic recrystallization with increasing SiCp size, and the dynamic recrystallization occurred more easily at higher temperatures and lower strain rates. Consequently, the instability zones of the composites are all mainly located in the deformation region with lower temperature and higher strain rate, and smaller SiCp results in larger instability zones.

Recent Uses of Paper Microfluidics in Isothermal Nucleic Acid Amplification Tests.

Isothermal nucleic acid amplification tests have recently gained popularity over polymerase chain reaction (PCR), as they only require a constant temperature and significantly simplify nucleic acid amplification. Recently, numerous attempts have been made to incorporate paper microfluidics into these isothermal amplification tests. Paper microfluidics (including lateral flow strips) have been used to extract nucleic acids, amplify the target gene, and detect amplified products, all toward automating the process. We investigated the literature from 2020 to the present, i.e., since the onset of the COVID-19 pandemic, during which a significant surge in isothermal amplification tests has been observed. Paper microfluidic detection has been used extensively for recombinase polymerase amplification (RPA) and its related methods, along with loop-mediated isothermal amplification (LAMP) and rolling circle amplification (RCA). Detection was conducted primarily with colorimetric and fluorometric methods, although a few publications demonstrated flow distance- and surface-enhanced Raman spectroscopic (SERS)-based detection. A good number of publications could be found that demonstrated both amplification and detection on paper microfluidic platforms. A small number of publications could be found that showed extraction or all three procedures (i.e., fully integrated systems) on paper microfluidic platforms, necessitating the need for future work.

Recovery of LiCl and Co3O4 from the cathode material contained in spent lithium-ion batteries using chlorination roasting with MgCl2·6H2O

Highly demanded lithium and cobalt are considered critical metals because their reserves in the earth’s crust are relatively low in abundance, and they are found in a few countries. Thus, the extraction of these metals from spent lithium-ion batteries (LIBs) has gained much attention since they are present in relatively high concentrations in the cathode of the battery. Chlorination roasting is an attractive technique of metal extraction because of its salient features: short reaction times and moderate reaction temperatures, selectivity to the extraction of certain metals and in many cases implies the use of low-cost chlorinating reactants. However, there are few studies concerning the recycling of metals through chlorination roasting. This research paper evaluates the chlorination roasting using MgCl2·6H2O as chlorinating reactant followed by water-leaching to recycle lithium and cobalt from the cathode material of spent LIBs. First, a non-isothermal chlorination test between 20 and 900 °C was performed to evaluate how temperature affects the chlorination of the metals and the presence of impurities. Then, isothermal chlorination tests at 420, 440 and 470 °C for times between 60 and 350 min were performed to evaluate the effect of time on the purity of the product. It was found that the chlorination treatment is selective to lithium. HCl(g) generated during the decomposition of MgCl2·6H2O reacts with lithium to produce LiCl. Cobalt is extracted as Co3O4, as it is another product of the chlorination reaction. The product of LiCl impurified with Mg(OH)Cl, formed during the extraction process, was purified by a heat treatment in air at 570 °C for 60 min followed by water-leaching. This treatment also generates MgO as a by-product. The optimum conditions of the extractive process were the followings: 440 °C and 210 min. The extraction yields of lithium and cobalt were 83.29% and 89.66%, respectively. The recycling process proposed here proved to be efficient. Moreover, the magnesium chloride generated as waste from the lithium extraction process from brines could be applied in the process from a circular economy point of view.

Measurement and modeling of peroxides half‐life: A thermo‐kinetic approach

AbstractHalf‐life values of organic peroxides at elevated temperature conditions are important in characterizing the reactivity and are often available in literature or through vendors. However, there is often lack of details/accuracy on methods used to obtain these values, as well as differences in methods across vendors and publications, thus resulting in discrepant reactivity profile. To address this, a method involving calorimetric experiment and thermo‐kinetic modeling was developed. The current approach was applied on five peroxides samples to obtain kinetic parameters and estimate their half‐life in the temperature range of interest. The measurements were performed by DSC under non‐isothermal conditions on the dilute peroxide solutions (∼0.12 M in mineral oil) and the data were kinetically treated according to three model‐based and one model‐free kinetic equations. A very good agreement was found between the half‐life calculated by all kinetic methods, but significant differences were noticed with the kinetic parameters reported in literature. Additionally, the obtained half‐life results, based on non‐isothermal measurements developed kinetic models, were validated through isothermal calorimetric testing. Given the accuracy and robustness of our results, the current method can be applied to estimate half‐life of organic peroxides at elevated temperature conditions.

Deep learning-assisted calculation of apparent activation energy for cement-based systems incorporating microencapsulated phase change materials

Sustained efforts have been directed towards understanding the effects of microencapsulated phase change materials (MPCMs) on the microstructural and mechanical strength development of portland cement-based systems. Yet, the sensitivity of the hydration reaction kinetics of MPCM-integrated cementitious systems to temperature remains largely unexplored. This study proposes a deep learning framework to simulate the hydration process and calculate the apparent activation energy of such cementitious composites. Extensive isothermal calorimetry tests were carried out to compile a robust time-dependent dataset for developing various pertinent machine learning models. Initially, it was demonstrated that the deep neural network outperformed the gradient boosting ensemble in predicting the hydration rate and cumulative heat. Furthermore, the hydration parameters and apparent activation energy of diverse cement-based systems incorporating MPCMs were calculated based on the predictions of the deep learning model. It was found that the addition of MPCMs at 10 and 20 wt% of cement reduced the apparent activation energy by nearly 10% and 28%, respectively, indicating less sensitivity of the hydration reactions to temperature. Ultimately, the results of this study can help better understand the effects of high-temperature curing on mechanical strength development and calculate the temperature-related stresses and potential thermal cracking in hydrating concretes made with MPCM inclusions.

Adsorption of total petroleum hydrocarbon in groundwater by KOH-activated biochar loaded double surfactant-modified nZVI

Introduction: Crude oil and petroleum hydrocarbon contamination is commonly found in the soil and groundwater during the various processes of mining, processing, and utilization due to issues such as inefficient environmental management, random wastewater discharge, and storage tank leakage.To address this issue, we will use corn stalk biochar (SBC) and surfactants to improve the stability and chemical reactivity of nZVI, thereby enhancing its ability to remove pollutants, and explore the adsorption effect and mechanism of composite materials for petroleum hydrocarbons.Methods: Modified corn stalk biochar (SBC) was synthesized through high-temperature carbonization and KOH activation. Subsequently, the iron/carbon composite PN-nZVI@SBC (PNMSBC) was prepared by loading nano zero-valent iron modified with dual surfactants, and it was adopted to adsorb total petroleum hydrocarbons(TPH) in groundwater. The physical and chemical properties, surface patterns, and elemental mapping of PNMSBC particles were analyzed using SEM, EDS, TEM,XRD, BET, and FTIR spectroscopy. Kinetics and isotherm tests were performed to evaluate the adsorption properties of the composites. TPH adsorption was dependent on ionic strength, initial TPH concentration, as well as pH. The adsorption mechanism combining XPS and EPR spectroscopy was explored.Results: The characterization results by SEM and TEM showed that the particle size of nZVI particles modified by surfactants became smaller, and the dispersibility was enhanced. The characterization results by XRD and FTIR confirmed the successful preparation of the composites. The BET results showed that MSBC and PNMSBC were mesoporous structures. The characterization results indicated that Polyvinylpyrrolidone (PVP) and Sodium oleate (NaOA) inhibited the oxidation of nZVI while effectively improving its reactivity. The result of the experiments on adsorption showed that the removal of TPH by PNMSBC followed Freundlich isotherm and pseudo-second-order kinetic models, thus suggesting that the main adsorption processes comprise chemisorption and multilayer heterogeneous adsorption. The adsorption capacity of PNMSBC was increased by the abundance of macro and microporous structures. To be specific, a maximum Langmuir adsorption capacity (qm) was achieved as 75.26 g/g. The result of batch experiments indicated that PNMSBC continuously removed considerable TPH under a wide pH range from 2 to 6. The adsorption mechanism of PNMSBC includes surface adsorption, oxidation, complexation, and electrostatic interaction.Discussion: In brief, PNMSBC has a promising application for the adsorption of TPH in groundwater remediation.

Research on Thermal Properties and High Temperature Exposure Behavior of Non-Skid Coating Fabricated by Twin Wire Arc Spraying

Conventional non-skid coatings for marine construction contain polymeric materials. These materials are generally susceptible to high temperature environments because of their low thermal conductivity and thermal resistance. A metal-based non-skid coating has great potential for high temperature applications, yet, there has only been limited research. In this study, twin wire arc spray (TWAS) was used to fabricate Al and Al-3%Ti coatings on a high strength low alloyed (HSLA) steel substrate. The purpose of this study is to confirm the feasibility of TWAS Al-based coating for non-skid areas on marine construction. The static coefficient friction of TWAS Al-based coatings exhibited excellent and uniform values compared with a conventional epoxy-based non-skid coating. The specific heat and thermal conductivity of TWAS Al-based coating was measured and compared with that of the substrate. The thermal property values of the TWAS Al-based coating were reported for the first time in this study. The TWAS Al-based coating had A continuous interface with the substrate and the general microstructural features of a thermal-sprayed metal coating. After exposure to 500℃ for 24 hours, the an Fe-Al intermetallic compound and oxide were formed inside of the coating and coating-substrate interface. The adhesion strength indicated that the TWAS Al-based coating sustained its strength after the isothermal exposure test. The Vickers hardness of the TWAS Al-3%Ti coating was higher than that of the Al coating. The solid solution hardening of Ti atoms in the as-deposited coating and the precipitation hardening of the TiAl3 compound in the heat-treated coating contributed to the improvement of in Vickers hardness. Thus, the TWAS Al-3%Ti coating is proven to be a promising nonskid coating for high temperature applications.

Hot deformation behaviour and optimization of process parameters for an as-cast Cu–20Ni–20Mn alloy

The hot deformation behaviour of an as-cast Cu–20Ni–20Mn alloy was investigated by isothermal compression tests in a TA-DIL 805 phase change thermal expansion instrument with a temperature ranging from 800 to 950 °C and a strain-rate ranging from 0.001 s−1 to 1 s−1. The results showed that Cu–20Ni–20Mn presented a stress drop at the beginning of the strain, and the flow stress decreased with increasing temperature and decreasing of strain rate. In particular, the hot deformation activation energy was determined to be 277.958 kJ/mol. The hot compression constitutive equation was established, and the processing maps of the alloy were constructed. The stress-strain values predicted by the proposed model were coincident with the experimental results, which confirmed that the deformation principal equation gives an accurate and precise estimate of the flow stress in Cu–20Ni–20Mn. The established processing maps and microstructure analysis determined the rolling process parameters in which the optimum range of temperature for the hot-working deformation of the as-cast Cu–20Ni–20Mn alloy is 810–900 °C with a strain rate of 0.001–0.002 s−1.

Thermomechanical characterization and conventional rolling of a novel β-solidifying γ-TiAl alloy with excellent comprehensive properties

The development of the β-solidifying γ-TiAl alloys with good oxidation resistance and thermal deformation ability has always been crucial for the practical application. However, increasing the content of the antioxidant elements, such as Nb, Al, etc., tends to be detrimental to the deformability of the alloys. In this work, a novel Nb, Mn containing β-solidifying TiAl alloy with the nominal composition of Ti-43Al-1.5Mn-3Nb-0.2C-0.2Si-0.1B (at. %) (named as NbMn-TiAl) is invented, which goes through the single β phase as well as the α phase during solidification, resulting in the final as-cast microstructure of nearly full lamellar structure (NFL). Subsequently, the isothermal compression tests were performed within a temperature range of 1100 °C–1300 °C and a strain rate range of 0.001 s−1-10 s−1, the hot processing maps and constitutive equation were established. Moreover, the deformation mechanisms were clarified, including the bending/kinking of the α2/γ lamellar colonies, the dynamic recrystallization (DRX) of γ phase and α phase at different temperatures. Rolled bars with a diameter of 12 mm were then directly fabricated from the ingot by conventional hot rolling process. The as-rolled bars exhibited excellent oxidation resistance and mechanical properties that outperform many available TiAl alloys manufactured using various methods.

Hot deformation behavior of Ni61Fe10Cr10Al17Mo2 high-entropy alloy with hierarchical structure

The Ni61Fe10Cr10Al17Mo2 high-entropy alloys (HEAs) with low density have been developed with great potentials for applications. The forging process is one of the important methods for fabricating components. Accordingly, the study of the deformation behavior of HEAs is the essence in the processing and molding of this material for using in industry. Moreover, there are multiple phases with hierarchical structures in the as-cast Ni61Fe10Cr10Al17Mo2 alloys, with the face-centered cubic (FCC) phase as the matrix phase accompanied with hard body-centered cubic (BCC) B2 phase. Here, the hot deformation behaviors of the homogenized Ni61Fe10Cr10Al17Mo2 alloy were investigated at strain rates ranging from 0.001 to 1.0 s−1 and temperatures ranging from 1000 to 1200 °C via isothermal compression tests. The true stress-strain curves were used to reveal the relationship between the flow stress and the deformation temperature and strain rate. The constitutive equations describing the correlations between the flow stress and hot compression parameters were constructed. At the same time, the dynamic material model and instability criterion were used to plot the hot processing map. Furthermore, the deformed microstructures and the dynamic recrystallization of alloy were investigated. Combined with the processing map, the optimal processing route is obtained.

Sorption Kinects and Equilibrium for The Removal of Cadmium and Lead from Aqueous Phase on Rice Husk in Inverse Fluidization Technique

The objectives of this study are to use the inverse fluidization technique to remove heavy metals from wastewater using inexpensive agricultural waste (Rice Husks) and to investigate the effects of operating factors on the dynamic behavior of the adsorption procedure in the inverse fluidized bed, such as the mass of modified rice husks, flow rate (Q), and particle size (dp ). During batch experiments, the best metal ion removal effectiveness was found to be at pH 5, which was discovered after investigating several pH values to achieve this goal. The ideal shaking speed for batch adsorption was 180 rpm. Adsorption efficiency was seen to rise as contact time in the process increased, and the ideal contact time was 3 hours. According to the findings, Cd and Pb had high removal efficiencies from aqueous solutions, 96.83 percent and 91.90%, respectively. Continuous column experiments (inverse fluidized bed) were used to confirm the adsorbent loading capacities for cadmium and lead, which were evaluated by batch research. The proposed adsorbent’s highest adsorption capacity in a batch system was determined to be 7.38 mg/g for Cd and 6.93 mg/g for Pb. Three models-Temkin, Freundlich, and Langmuir-were fitted to a series of equilibrium isothermal tests. The Freundlich isotherm model, with correlation coefficients R2 of 0.98 for Pb and 0.97 for Cd, offered the best fit to the experimental data for this system. The rice husk equilibrium isotherms were determined to be of a favorite kind. To investigate the impact of initial concentrations, bed depth, flow rate, and particle size at a temperature of 30 on the effectiveness of the adsorption process, numerous experiments were conducted in an inverse fluidized bed column. According to the results, rice husk appears to be a material that shows promise for cleaning wastewater of contaminants and toxins.