Precipitation Phenomena Research Articles

On the work-hardening behaviour of the additively manufactured Al-Si-Mg alloys: composite-like versus networked microstructure

Al-Si-Mg alloys are widely used for manufacturing components via laser powder bed fusion in various industrial applications where ductility and the capacity to accommodate the strain hardening are key criteria. The ductility of the laser powder bed-fused Al alloys has become a crucial property due to their fine cellular microstructure. Post-processing heat treatments improve ductility, but resultant microstructural changes affect the work-hardening behaviour, deformability, and uniform elongation values. This study aims to investigate the work-hardening capability, uniform elongation and deformability of AlSi7Mg and AlSi10Mg samples after different post-processing heat treatments by using tensile tests, optical and scanning electron microscopies. At aging temperatures below 200°C, the fully cellular structure of eutectic Si governs both the work-hardening behaviour and the strengthening mechanisms, despite the precipitation phenomenon. When direct-aging temperatures exceed 200°C, the coarsening of the Si-eutectic network modifies work-hardening behavior (Stages 1-3), accentuating the effects induced by the precipitates. Artificial aging highlights the role of precipitates in controlling both work-hardening properties and deformability.

A Concept of Local Coordination Number for the Characterization of Solute Clusters within Atom Probe Tomography Data.

Identifying clusters of solute atoms in a matrix of solvent atoms helps to understand precipitation phenomena in alloys, for example, during the age hardening of certain aluminum alloys. Atom probe tomography datasets can deliver such information, provided that appropriate cluster identification routines are available. We investigate algorithms based on the local composition of the neighborhood of solute atoms and compare them with traditional approaches based on the local solute number density, such as the maximum separation distance method. For an ideal solid solution, the pair correlation functions of the kth nearest solute atom in the coordination number representation are derived, and the percolation threshold and the size distribution of clusters are studied. A criterion for selecting optimal control parameters based on maximizing the phase separation by the degree of clustering is proposed for a two-phase system. A map of phase compositions accessible for cluster analysis is constructed. The coordination number approach reduces the influence of density variations commonly observed in atom probe tomography data. Finally, a practical cluster analysis technique applied to the early stages of aluminum alloy aging is described.

Optimizing Tempering Parameters to Enhance Precipitation Behavior and Impact Toughness in High-Nickel Steel

This study explores the effects of tempering on the precipitation behavior and impact toughness of high-nickel steel. The specimens underwent double quenching at 870 °C and 770 °C, followed by tempering at various temperatures. Advanced characterization techniques including optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to elucidate precipitation phenomena. Additionally, electron backscatter diffraction (EBSD) was employed to assess the misorientation distribution after tempering. Charpy impact tests were performed on specimens tempered at different temperatures to evaluate their toughness. The findings reveal that with increasing tempering temperature, the fraction of low-angle grain boundaries decreases, which correlates positively with enhanced impact toughness. The results demonstrate that tempering at 580 °C optimizes the material’s microstructure, achieving an impact toughness value of approximately 163 J.

Study on the micro-rheological properties of fly ash-based cement mortar

Aiming at the shortcomings of poor rheological properties and low strength of tailings filling mortar, solid waste materials such as fly ash, steel slag, and desulfurization ash were introduced to improve the filling mortar. The Response Surface Methodology (RSM) was used to design the test ratios to determine the significance of the effect of fly ash, steel slag and desulphurization ash on the physical properties of the mortar. The rheological characterization law of filling mortar was studied based on macroscopic L-tube test. The mechanism of filling mortar improvement was analyzed by Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS) and other microscopic tests. The results show that the response-factor model fit regression is significant, with the highest model satisfaction at 12 % fly ash dosing, 15 % steel slag dosing, and 10 % desulfurization ash dosing. The self-flowing extension diameter of the mortar is 15.34 cm, and the 3d and 28d strengths are 0.58 MPa and 3.24 MPa, respectively. Fly ash has effectively improved the phenomenon of mortar segregation and precipitation, and the yield stress of mortar is reduced by 35.1∼64.9 % when the dosage is 8∼12 %. The fractal dimension and mortar workability are positively correlated with fly ash admixture. Fly ash incorporation will gradually consume the calcium hydroxide (CH) to generate alumina ferrite (Aft) and calcium silicate hydrate (C-S-H), which reduces mortar porosity and promotes long-term strength growth. The research results not only realized the effective utilization of solid waste resources, but also significantly improved the performance of the filler and ensured the safe production of the mine.

Understanding the differential precipitation behavior of friction stir welded Al-Zn-Mg-Fe alloy during long-term natural aging

Al-Zn-Mg-Fe (HE700) is a new generation cast alloy based on dilute Al-Fe hypoeutectic system. Being a new member, the precipitation behavior of the HE700 alloy is not fully understood unlike its conventional 7xxx series counterparts. Moreover, presence of Fe and friction stir welding (FSW) used to join such alloys add to the complexity of the precipitation phenomenon. The present study captured the microstructural features with atomic-scale resolution that provided new insights into the nature, distribution, and evolution of precipitates in this alloy. The stir zone (SZ) and heat-affected zone (HAZ) exhibited significantly different natural aging behavior. Finer precipitates identified as GPI and GPII (Guinier Preston zones) were found to coexist with very fine zinc-rich solute clusters in the SZ. The GP zones evolved gradually and transitioned into strengthening precipitates. The HAZ, on other hand, exhibited heterogeneous distribution of coarse pre-existed particles and fine MgZn2 precipitates that were heterogeneously nucleated by localized solute supersaturation and thermally induced dislocations. Hardness variations can be correlated to precipitates evolution thereby helping design a suitable post-weld heat treatment (PWHT) process.

Assessment of subcutaneously administered insulins using in vitro release cartridge: Medium composition and albumin binding

Biotherapeutics is the fastest growing class of drugs administered by subcutaneous injection. In vitro release testing mimicking physiological conditions at the injection site may guide formulation development and improve biopredictive capabilities. Here, anin vitrorelease cartridge (IVR cartridge) comprising a porous agarose matrix emulating subcutaneous tissue was explored. The objective was to assess effects of medium composition and incorporation of human serum albumin into the matrix. Drug disappearance was assessed for solution, suspension and in situ precipitating insulin products (Actrapid, Levemir, Tresiba, Mixtard 30, Insulatard, Lantus) using the flow-based cartridge. UV–Vis imaging and light microscopy visualized dissolution, precipitation and albumin binding phenomena at the injection site. Divalent cations present in the release medium resulted in slower insulin disappearance for suspension-based and in situ precipitating insulins. Albumin-binding acylated insulin analogs exhibited rapid disappearance from the cartridge; however, sustained retention was achieved by coupling albumin to the matrix. An in vitro-in vivorelation was established for the non-albumin-binding insulins.The IVR cartridge is flexible with potential in formulation development as shown by the ability to accommodate solutions, suspensions, and in situ forming formulations while tailoring of the system to probe in vivo relevant medium effects and tissue constituent interactions.

Innovative insights into the preparation of tamarind gum base film loaded with pomelo essential oil via a low-energy emulsion method combined with melatonin: Maximizing the dual functions of tamarind gum

Pomelo essential oil has good antioxidant and antimicrobial properties. The objective of this study was to modify the active packaging loaded with essential oil through low-energy emulsification, in order to achieve both film-forming and emulsifying properties of tamarind gum, and to investigate the surface activity of melatonin in the emulsion. When α:β mixing ratio of 60:40, the resulting film solution exhibited favorable apparent viscosity and reduced emulsion flocculation and precipitation phenomena. Particle size distribution analysis and optical microscopy results demonstrated that the obtained emulsion was uniformly dispersed at an α:β mixing ratio of 60:40, with droplet diameters mainly concentrated within the range of 1–100 μm. After undergoing film-forming treatment, E-3-F (α:β mixing ratio of 60:40) exhibited a smoother and more compact microstructure, leading to significant improvements in mechanical properties and barrier performance. Laser confocal microscopy imaging revealed that the addition of melatonin further reduced interfacial tension between oil and water, while simultaneously weakening hydrophobic interaction forces among oil droplets, thereby effectively inhibiting droplet aggregation behavior. Moreover, incorporation of melatonin also enhanced material compactness and imparted excellent antioxidant effects to the packaging material. Consequently, this study ultimately unveils potential for low-energy emulsification combined with melatonin application in bio-based packaging field while providing novel insights into developing multifunctional bio-based packaging.

Transparent and High-Refractive-Index Titanium Dioxide/Thermoplastic Polyurethane Nanocomposites.

Transparent nanocomposite films made of surface-modified titanium dioxide nanoparticles and thermoplastic polyurethane are prepared via film casting approach showing enhanced refractive indexes and mechanical properties. Two different sets of composites were prepared up to 37.5 wt % of inorganic nanoparticles with a diameter <15 nm, one set using particles capped only with oleic acid and a second one with a bimodal system layer made of oleic acid and mPEO-5000 as coating agents. All of the composites show significantly enhanced refractive index and mechanical properties than the neat polymeric matrix. The transparency of nanocomposite films shows the excellent dispersion of the inorganic nanoparticles in the polymeric matrix avoiding aggregation and precipitation phenomena. Our study provides a facile and feasible route to produce transparent nanocomposite films with tunable mechanical properties and high refractive indices for various applications.

Tempering of Dual Phase steels: Microstructural evolutions and mechanical properties

Modelling the microstructural evolutions and mechanical properties during the tempering of Dual Phase steels is a key objective for industrials as this phenomenon has a strong impact on the final properties. After having determined the tempering kinetics of fully martensitic steels between 100°C and 550°C using thermoelectric Power and hardness measurements, time–temperature equivalences were applied to determine the activation energies of the mechanisms controlling martensite tempering. Two tempering stages were clearly identified and thanks to the use of TEM, SEM and tomography techniques, they could be attributed to cementite precipitation, its spheroidization and recovery phenomena. The second stage was found to be retarded with increasing the manganese content of the steel contrary to the first stage. From these studies, a JMAK model was developed to predict the microstructurals evolutions during tempering. Then, an extension of the Hybrid-mean Field Composite model developed in a previous paper to predict the tensile curves of fresh martensite was proposed to take into account the microstructural evolutions of martensite during tempering. The model was tested for a wide range of physical parameters of the microstructure (phase fraction and chemical composition) and for different tempering heat treatments and gave good agreement with experimental tensile curves.

High‐Precision Dilatometry for the Study of Precipitation Processes and Microalloying Effects in Lightweight Alloys ‐ A Specific Review

By dilatometry, the absolute change in the length of a sample is measured. As length, i.e., volume, is a state variable, its change can be monitored for long time ranges. This is the decisive advantage compared to the widely applied calorimetric methods which are based on a rate (change of heat) and where the maximum time range is determined by the resolution limit of the heat flow measurement. In contrast, if the measurement environment is kept at a constant temperature, dilatometric signals can be measured for very long time ranges down to very small changes with resolution in the nm range. The application of high‐stability isothermal dilatometry for studying precipitation phenomena in Al(Mg,Si)‐, Ti(V)‐, and Ti(Cr)‐alloys is summarized in the present review. Al(Mg,Si) turns out as a prime example where the various phases can unambiguously be distinguished by their characteristic length change features. For Ti(V), the influence of the oxygen impurity on the omega phase formation, and for Ti(Cr), the effect of Sn alloying on the omega phase formation can be revealed by dilatometry. The results on Al(Mg, Si) are compared with dilatometry on Al(Cu)‐alloys upon time‐linear heating, for which also the effect of microalloying with Au is studied.

Influence of sample extraction location on thermal desorption spectroscopy from a heat-resistant 13CrMo4-5 steel plate and correlation with microstructure features

Thermal desorption spectroscopy (TDS) is a highly sensitive and widely used method to directly measure the total hydrogen concentration and indirectly assess the hydrogen trapping sites and mechanisms from the spectra features in steels. Thus, there is a need to investigate the influence of sample location from a 5 mm plate of hot-rolled heat-resistant structural steel on TDS spectra. Via a new highly sensitive and specific correlation coefficient (microToH), the TDS results are correlated with low-angle grain boundaries volume fraction, grain size with different misorientation thresholds, microhardness, and geometrically necessary dislocations at different densities.The results indicate that sample location influences 133 % and 62 % in the hydrogen desorption of peak 1 (at 515 K), and total hydrogen concentration via the influence of peak 2 (at 634 K), respectively. Thus, sample location needs to be considered as one relevant aspect in a research plan based on TDS analysis. The influence on peak 3 (at 762 K) was found to be negligible as it is related to the first exothermic peak of the heating cycle, associated with carbide precipitation phenomena. The individual grain analysis performed with high-resolution adaptive DMM and GND maps emphasises the accumulation of the deformation in the ferritic domain at the vicinity of the pearlite structures.

Nanofluidic Study of Multiscale Phase Transitions and Wax Precipitation in Shale Oil Reservoirs

During hydraulic fracturing of waxy shale oil reservoirs, the presence of fracturing fluid can influence the phase behavior of the fluid within the reservoir, and heat exchange between the fluids causes wax precipitation that impacts reservoir development. To investigate multiscale fluid phase transition and microscale flow impacted by fracturing fluid injection, this study conducted no-water phase behavior experiments, water injection wax precipitation experiments, and water-condition phase behavior experiments using a nanofluidic chip model. The results show that in the no-water phase experiment, the gasification occurred first in the large cracks, while the matrix throat was the last, and the bubble point pressure difference between the two was 12.1 MPa. The wax precipitation phenomena during fracturing fluid injection can be divided into granular wax in cracks, flake wax in cracks, and wax precipitation in the matrix throat, and the wax mainly accumulated in the microcracks and remained in the form of particles. Compared with the no-water conditions, the large cracks and matrix throat bubble point in the water conditions decreased by 6.1 MPa and 3.5 MPa, respectively, and the presence of the water phase reduced the material occupancy ratio at each pore scale. For the smallest matrix throat, the final gas occupancy ratio under the water conditions decreased from 32% to 24% in the experiment without water. This study provides valuable insight into reservoir fracture modification and guidance for the efficient development of similar reservoirs.

Influence of heat treatments on low-power-LPBFed CuCrZr for nuclear fusion applications

In this study, the processability of CuCrZr alloy with additive manufacturing (AM) technology and the performance achievable with Direct Age Hardening treatments for nuclear fusion applications were investigated. This copper alloy is one of the most interesting for the field: it is easier to manufacture through Laser-based additive manufacturing technology and mechanically superior compared to pure copper, and it ensures values of thermal conductivity high enough to be considered a valid substitute for pure copper in many applications.The investigation on CuCrZr alloy was carried out in order to examine the influence of Direct Age Hardening (DAH) treatments on physical and mechanical properties. Laser Powder Bed Fusion technology was used to produce samples with CuCrZr alloy. The additive manufacturing process involved a machine provided with a 370 W IR laser and a preliminary process optimization was carried out to find the printing parameters that assured the highest density (99.15 %), which confirmed the processability of CuCrZr alloy also with low IR laser power. Then, three different DAH treatments were tested and the performance of DAHed material was compared to that of the alloy in as-built conditions. Precipitation phenomena were investigated with DSC analyses, revealing the effectiveness of the treatment already after 1 h. A deep microstructural investigation revealed a fine cellular structure formed during solidification and the presence of nanometric precipitates starting from the as-built condition. The presence of microstructural defects was also investigated. Mechanical performance and thermal conductivity were tested, too: the as-built samples showed limited properties, while very promising results for the use of additively manufactured CuCrZr components have been obtained after the DAHs. The ultimate tensile strength (UTS) and yield strength (YS) doubled the as-built values after 1 h treatment at 550 °C. The thermal conductivity reached three times the initial condition (from 100 W/mK to 300 W/mK).

Simultaneous removal of ammonia nitrogen, calcium and cadmium in a biofilm reactor based on microbial-induced calcium precipitation: Optimization of conditions, mechanism and community biological response

With the enhancement of environmental governance regulations, the discharge requirements for reverse osmosis wastewater have become increasingly stringent. This study proposes an innovative approach utilizing heterotrophic nitrification and aerobic denitrification (HNAD)-based biomineralization technology, combined with coconut palm silk loaded biochar, to offer a novel solution for resource-efficient and eco-friendly treatment of reverse osmosis wastewater. Zobellella denitrificans sp. LX16 were loaded onto modified coir silk and showed removal efficiencies of up to 97.38, 94.58, 86.24, and 100% for NH4+-N (65 mg L−1), COD (900 mg L−1), Ca2+ (180 mg L−1), and Cd2+ (25 mg L−1). Analysis of the metabolites of microorganisms reveals that coconut palm silk loaded with deciduous biochar (BCPS) not only exerts a protective effect on microorganisms, but also enhances their growth, metabolism, and electron transfer capabilities. Characterization of precipitation phenomena elucidated the mechanism of Cd2+ removal via ion exchange, precipitation, and adsorption. Employing high-throughput and KEGG functional analyses has confirmed the biota environmental response strategies and the identification of key genes like HNAD.

First Results From REPTile‐2 Measurements Onboard CIRBE

AbstractCIRBE (Colorado Inner Radiation Belt Experiment), a 3U CubeSat, was launched on 15 April 2023 into a sun synchronous orbit (97.4° inclination and 509 km altitude). The sole science payload onboard is REPTile‐2 (Relativistic Electron and Proton Telescope integrated little experiment—2), an advanced version of REPTile which operated in space between 2012 and 2014. REPTile‐2 has 60 channels for electrons (0.25–6 MeV) and 60 channels for protons (6.5–100 MeV). It has been working well, capturing detailed dynamics of the radiation belt electrons, including several orders of magnitude enhancements of the outer belt electrons after an intense magnetic storm, multiple “wisps”‐ an electron precipitation phenomenon associated with human‐made very low frequency (VLF) waves in the inner belt, and “drift echoes” of 0.25–1.4 MeV electrons across the entire inner belt and part of the outer belt. These new observations provide opportunities to test the understanding of the physical mechanisms responsible for these features.

General Local Reactive Boundary Condition for Dissolution and Precipitation Using the Lattice Boltzmann Method

AbstractA general and local reactive boundary condition (RBC) for studying first‐order equilibrium reactions using the lattice Boltzmann method is presented. Its main characteristics are accurate reproduction of wall diffusion, invariance to the wall and grid orientation, and absence of nonphysical artifacts. The scheme is successfully tested for different benchmark cases considering diffusion, advection, and reactions of fluids at solid‐liquid interfaces. Unlike other comparable RBCs from the literature, the novel scheme is valid for a large range of Péclet and Damköhler numbers, and shows realistic pattern formation during precipitation. In addition, quantitative results are in good accordance with analytical solutions and values from literature. Combining the new RBC with the rest fraction method, Péclet‐Reynolds ratios of up to 1,000 can be achieved. Overall, the novel RBC accurately models first‐order reactions, is applicable for complex geometries, and allows efficiently simulating dissolution and precipitation phenomena in fluids at the pore scale.

Study on the actual particle size, activity concentration, and migration process adsorption behavior of radioactive substances in liquid effluents from nuclear power plants

Radionuclides emitted by nuclear power plants may have effects on the environment and public health. At present, research on radioactive material effluent in the industry mainly focuses on the treatment of radioactive effluent and the particle size distribution of the primary circuit. There is little research on the particle size of radioactive material during the migration process outside the primary circuit system, as well as the flocculation precipitation and other enrichment phenomena during the collection process of effluent. Therefore, this study relies on the sampling of effluent from an in-service nuclear power plant to measure its radioactivity level by particle size range. At the same time, the mixing process of effluent is simulated in the laboratory to simulate the adsorption behavior of effluent during the migration process. It was found that in the activity concentration of detectable radioactive nuclides in the effluent samples, more than 95% of radioactive nuclides exist in the liquid with particle sizes less than 0.1μm, while particle sizes greater than 0.45 μm account for less than 5%. After the sample was filtered by the demineralizer, the radioactive activity decreased. The flocculation precipitation in the waste liquid of the waste water recovery system has a certain contribution to the enrichment of nuclides. With the extension of time, the enrichment of transition elements such as cobalt and manganese is particularly obvious, so that it is distributed in the liquid again with a large particle size. In addition, large particle size substances such as colloids in seawater have a certain adsorption effect on radionuclides, which will lead to its aggregation effect again.

An Investigation into Microstructure Evolution and High-temperature Deformation Behavior during the Instability of In-service Welding

It is of great significance to reveal deformation behavior coupling with both the high-temperature effect and microstructure for the in-service welding instability zone. In the present paper, microstructure evolution and high-temperature deformation behavior at the representative temperatures 900 °C and 1100 °C inside the in-service welding instability zone were investigated based on the in-situ high-temperature laser scanning confocal microscope (LSCM). The results indicated that a sufficient condition of carbide precipitation is to hold it at 900 °C for a certain time. However, the phenomenon of carbide precipitation failed to be presented during continuous heating to 1150 °C. Although the slip and twining deformation occurred inside austenite grain, the fracture mechanism gave priority to intergranular cracking, which could be ascribed to the carbides with higher hardness and the grain boundary weakening caused by the temperature effect.

Valorization of Aloe vera waste for the production of Ca and P-rich hydrochars

The production of gel from Aloe vera plants is an emerging industry, however the residual leaves are considered waste and are not utilized. The purpose of this work was to prepare hydrochars from Aloe vera leaves under different conditions, and determine the fate of macro- and micronutrients in the solid products, in view of developing a novel biofertilizer. In this framework, distilled water, citric acid and potassium hydroxide solutions were used as feedwaters and the experiments were performed at the temperatures of 180 and 220 °C and treatment times of 1 – 8 h. All obtained hydrochars had increased Ca and P contents compared to the feedstock, whereas the highest Ca and P concentration of 10.4% and 7382 mg kg−1, respectively, were achieved under alkaline conditions after 8 h of treatment. Citric acid promoted carbonization, achieving H/C = 1.11, O/C = 0.34 of the hydrochar obtained at 220 °C after 8 h of treatment. The use of KOH counterbalanced the production of acids from the degradation of the biomass, thus restricting the carbonization progress. The metals K, Fe, Cu and Mg showed high solubilization tendencies, however their concentrations on the hydrochars increased beyond the 4 h treatments due to precipitation and re-sorption phenomena. The N content in the hydrochars ranged between 0.56 – 1.12%, increasing with temperature and time due to the formation and precipitation of pyridine, pyrroline and pyrrolidine derivatives. Overall, due to the high ash content, low pH and increased Ca and P concentrations, the hydrochars may be suitable as substrates for the development of bio-fertilizers purposed for alkaline soils.

Simulation of the Working Volume Reduction through the Bioconversion Model (BioModel) and Its Validation Using Biogas Plant Data for the Prediction of the Optimal Reactor Cleaning Period

The present study focuses on the working volume reduction of anaerobic reactors in biogas plants, which is caused by inorganic material accumulation and inadequate mixing and affects methane production and plant profitability. Precipitation phenomena lead to periodic reactor cleaning processes, which complicate the operation of the plant and increase its operating costs. For this purpose, the bioconversion model (BioModel) was utilized by modifying its conditions to accurately simulate the reduction of the working volume of a biogas plant facing precipitation problems for a study period of 150 days. The modified BioModel exhibited notable results in the prediction of methane production, with an average deviation of 1.97% from the plant’s data. After validation, based on the model results, an equation was set up to predict the optimal reactor cleaning period. Incidentally, the optimal cleaning time was calculated at 5.1 years, which is very close to the period during which the cleaning of the reactors of the studied biogas plant took place (5.5 years). The findings of this research showed that the modified BioModel, along with the developed equation, can be effectively used as a tool for the prediction of the optimal reactor cleaning period.