Effects of silicon content on microstructure and stress corrosion cracking resistance of 7050 aluminum alloy

Evolution of microstructure and stress corrosion cracking （SCC） susceptibility of 7050 aluminum alloy with 0.094%, 0.134% and 0.261% Si （mass fraction） in T7651 condition have been investigated. The results show that the area fraction of Mg2Si increases from 0.16% to 1,48% and the size becomes coarser, while the area fraction of the other coarse phases including Al2CuMg, Mg（Al,Cu,Zn）2 and A17Cu2Fe decreases from 2.42% to 0.78% with Si content increasing from 0.094% to 0.261%. The tensile strength and elongation of 7050-T7651 alloys is decreased with the increase of Si content by slow strain rate test （SSRT） in ambient air. However, electrical conductivity is improved and SCC susceptibility is reduced with the increase of Si content by SSRT in corrosion environment with 3.5% NaCl solution.

Silicon Mitigates Aluminum Toxicity of Tartary Buckwheat by Regulating Antioxidant Systems

Aluminum (Al) toxicity is a considerable factor limiting crop yield and biomass in acidic soil. Tartary buckwheatgrowing in acidic soil may suffer from Al poisoning. Here, we investigated the influence of Al stress on the growthof tartary buckwheat seedling roots, and the alleviation of Al stress by silicon (Si), as has been demonstrated inmany crops. Under Al stress, root growth (total root length, primary root length, root tips, root surface area, androot volume) was significantly inhibited, and Al and malondialdehyde (MDA) accumulated in the root tips. At thesame time, catalase (CAT) and ascorbate peroxidase activities, polyphenols, flavonoids, and 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free-radical scavenging abilitywere significantly decreased. After the application of Si, root growth, Al accumulation, and oxidative damage wereimproved. Compared to Al-treated seedlings, the contents of ·O2− and MDA decreased by 29.39% and 25.22%,respectively. This was associated with Si-induced increases in peroxidase and CAT enzyme activity, flavonoidcompounds, and free-radical scavenging (DPPH and ABTS). The application of Si therefore has positive effectson Al toxicity in tartary buckwheat roots by reducing Al accumulation in the roots and maintaining oxidationhomeostasis.

Hydrogen Content and Porosity Behavior of Hypereutectic Aluminum-silicon Alloy with Phosphorus

By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.

Influence of hydrogen content on the behavior of grain reflnement in hypereutectic aluminum-silicon alloy

Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationship between the initial hydrogen content inthe melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy wasinvestigated. The experimental results show that the cooling rate, the hydrogen content and thegrain refinement effect are three interactive factors. When the hydrogen content is above 0.20mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in thealloy melt influences the grain refinement effect. With increasing the cooling rate, the criticalhydrogen content increases too. It is expected that much hydrogen in the melt make the netinterfacial energy larger than or equal to zero, resulting in the shielding of the particles AlPduring solidification and that the critical gas content is closely related to the critical radius ofembryo bubbles.

Influence of Carbon Content on Element Diffusion in Silicon Carbide-Based TRISO Composite Fuel

The coating layers of Tri-structural Isotropic Particles(TRISO)serve to protect the kernel and act as barriers to fission products.Sintering aids in the silicon carbide matrix variably react with TRISO coating layers,leading to the destruction of the coating layers.Investigating how carbon content affects element diffusion in silicon carbide-based TRISO composite fuel is of great significance for predicting reactor safety.In this study,silicon carbide-based TRISO composite fuels with different carbon contents were prepared by adding varying amounts of phenolic resin to the silicon carbide matrix.X-ray Diffraction(XRD)and Scanning Electron Microscopy(SEM)were employed to characterize the phase composition,morphology,and microstructure of the composite fuels.The elemental content in each coating layer of TRISO was quantified using Energy-Dispersive X-ray Spectroscopy(EDS).The results demonstrated that the addition of phenolic resin promoted the uniform distribution of sintering aids in the silicon carbide matrix.The atomic percentage(at.%)of aluminum(Al)in the pyrolytic carbon layer of the TRISO particles reached its lowest value of 0.55%when the phenolic resin addition was 1%.This is because the addition of phenolic resin caused the Al and silicon(Si)in the matrix to preferentially react with the carbon in the phenolic resin to form a metastable liquid phase,rather than preferentially consuming the pyrolytic carbon in the outer coating layer of the TRISO particles.The findings suggest that carbon addition through phenolic resin incorporation can effectively mitigate the deleterious reactions between the TRISO coating layers and sintering aids,thereby enhancing the durability and safety of silicon carbide-based TRISO composite fuels.

Effect of water content on corrosion inhibition behavior of self-assembled TDPA on aluminum alloy surface

Self assembled monolayers （SAMs） of 1-tetradecylphosphonic acids （TDPA, CH3（CH2）13P（O）（OH）2 ） were formed on the 2024 aluminum alloy surface in TDPA-containing ethanol-water solutions with different water content. The adsorption and corrosion protection properties of the SAMs for 2024 alloy in 0.1 mol/L H2SO4 solution were examined and characterized by potentiodynamic polarization, electrochemical impedance spectrum （EIS）, Fourier transformed infrared spectroscopy （FTIR）, Auger electron spectra （AES） and atomic force microscopy （AFM）. FTIR and AES results show that the TDPA molecules were successfully adsorbed on the 2024 aluminum alloy surface, and the density of the SAMs increased with the increasing water content in the assembly solution. The results of electrochemical studies and corrosion morphologies observed by AFM show that a 4 h modification resulted in maximal inhibition efficiency, and the higher the water content in the assembly solution is, the better the inhibition performance of the SAMs can be achieved. The effect of water content in TDPA solutions on the performance of the SAMs is related to the hydration reaction of the metal surface.

Chaotic Identification and Prediction of Silicon Content in Hot Metal

The time series data of silicon content in hot metal were identified to have the chaotic feature because of the positive maximum Lyapunov exponent, and then the time scales to predict future were estimated. Finally a chaotic local-region model was constructed to predict silicon content in hot metal with good performance due to high hitting rate.

Pulsed Nd:YAG laser cladding of high silicon content coating on low silicon steel

A pulsed Nd：YAG （yttrium aluminum garnet） laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, with associated energy dispersive spectroscopy （EDS）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. The microhardness was also measured along the depth direction of the specimens, A crack- and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized single-track and multi-track laser cladding. The phases of the coating are a-Fe, T-Fe, and FeSi. The high microhardness of the lasercladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt% in the single-track cladding and 6.5wt% in the multi-track cladding, respectively.

Rapid Determination of Silicon Content in Rice

A method for rapid determination of silicon content in rice was introduced. The reliability of this method was verified by using a recombinant inbred line （RIL） population of rice cross Zhenshan 97B / Milyang 46. Two hundred and forty-nine RILs were transplanted in two replications. Simple correlation coefficients on the silicon content in the hull, flag leaf and stern in rice between duplicate samples of 498 rice materials were 0.97954, 0.97026 and 0.98848, respectively. Ten representative samples were selected for measurement using the high-temperature alkaline fusion method. Simple correlation coefficient between the silicon contents determined by the high-temperature alkaline fusion method and by the present method is 0.9993.

Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe- 2Cu-0.4Mg-1.0Ni-0.5Mn （mass fraction, %） alloy produced by semi-solid rheo-diecasting were studied. The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration （DUV） which was imposed on the alloy near the liquidus temperature for about 2 rain. Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting. The results show that the DUV treatment suppresses the formation of needle-like ,β-Al5（Fe,Mn）Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al4（Fe, Mn）Si2 particles. Additionally, the primary Si grows up as fine and round particles with uniform distribution in α（Al） matrix of this alloy under DUV treatment. The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively. The coefficient of thermal expansion （CTE） between 25 ℃ and 300 ℃ is 16.052 8×10^-6 ℃^-1, and the wear rate is 1.55%. The hardness of this alloy with 2% Fe reaches HB146.3. It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.

Fuzzy Prediction of Silicon Content for BF Hot Metal

Some key operation variables influencing hot metal silicon content were selected, and time lag of each of them was obtained. A standardized fuzzy system model was developed to approach the random nonlinear dynamic system of the change of silicon content, forecast the change of silicon content and calculate silicon content. The prediction of hot metal silicon content is very successful with the data collected online from BF No. 1 at Laiwu Iron and Steel Group Co.

Effect of Si content on interfacial reaction and properties between solid steel and liquid aluminum

The effect of Si content on the microstructures and growth kinetics of intermetallic compounds(IMCs)formed during the initial interfacial reaction(<10 s)between solid steel and liquid aluminum was investigated by a thermophysical simulation method.The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing.The results showed that IMCs layers mainly consisted ofη-Fe_(2)Al_(5)andθ-Fe_(4)Al_(13).The addition of Si reduced the thickness of the IMCs layer.The growth of theηphase was governed by the diffusion process when adding 2 wt.%Si to the aluminum melt.When 5 wt.%or 8 wt.%Si was added to aluminum,the growth was governed by both the diffusion process and interfacial reaction,and ternary phaseτ1/τ9-(Al,Si)_(5)Fe_(3)was formed in theηphase.The apparent activation energies of theηphase decreased gradually with increasing Si content.The joint with pure aluminum metal had the highest tensile strength and impact energy.

A chaos genetic algorithm for optimizing an artificial neural network of predicting silicon content in hot metal

A genetic algorithm based on the nested intervals chaos search (NICGA) hasbeen given. Because the nested intervals chaos search is introduced into the NICGA to initialize thepopulation and to lead the evolution of the population, the NICGA has the advantages of decreasingthe population size, enhancing the local search ability, and improving the computational efficiencyand optimization precision. In a multi4ayer feed forward neural network model for predicting thesilicon content in hot metal, the NICGA was used to optimize the connection weights and thresholdvalues of the neural network to improve the prediction precision. The application results show thatthe precision of predicting the silicon content has been increased.

An Improved Artificial Neural Network Model for Predicting Silicon Content of Blast Furnace Hot Metal

Based on the skills of initializing weight distribution, adding an impulse in a neural network and expanding the ideal of plural weights, an artificial neural network model with three connection weights between one and another neural unit was established to predict silicon content of blast furnace hot metal. After the neural network was trained in the off-line state on the basis of a large number of practical data of a commercial blast furnace and making many learning patterns, satisfactory testing and simulating results of the model were obtained.

New insights into the effects of silicon content on the oxidation process in silicon-containing steels

Simultaneous thermal analysis（STA） was used to investigate the effects of silicon content on the oxidation kinetics of silicon-containing steels under an atmosphere and heating procedures similar to those used in industrial reheating furnaces for the production of hot-rolled strips. Our results show that when the heating temperature was greater than the melting point of Fe2SiO4, the oxidation rates of steels with different silicon contents were the same; the total mass gain decreased with increasing silicon content, whereas it increased with increasing oxygen content. The oxidation rates for steels with different silicon contents were constant with respect to time under isothermal conditions. In addition, the starting oxidation temperature, the intense oxidation temperature, and the finishing oxidation temperature increased with increasing silicon content; the intense oxidation temperature had no correlation with the melting of Fe2SiO4. Moreover, the silicon distributed in two forms： as Fe2SiO4 at the interface between the innermost layer of oxide scale and the iron matrix, and as particles containing silicon in grains and grain boundaries in the iron matrix.

Microstructural analyses of aluminum–magnesium–silicon alloys welded by pulsed Nd: YAG laser welding

Revealing grains and very fine dendrites in a solidified weld metal of aluminum–magnesium–silicon alloys is difficult and thus,there is no evidence to validate the micro-and meso-scale physical models for hot cracks. In this research, the effect of preheating on the microstructure and hot crack creation in the pulsed laser welding of AA 6061 was investigated by an optical microscope and field emission electron microscopy. Etching was carried out in the gas phase using fresh Keller’s reagent for 600 s. The results showed that the grain size of the weld metal was proportional to the grain size of the base metal and was independent of the preheating temperature. Hot cracks passed the grain boundaries of the weld and the base metal. Lower solidification rates in the preheated samples led to coarser arm spacing;therefore, a lower cooling rate. Despite the results predicted by the micro and meso-scale models, lower cooling rates resulted in increased hot cracks. The cracks could grow in the weld metal after solidification;therefore, hot cracks were larger than predicted by the hot crack prediction models.

Synthesis and Characterization of Mesoporous Silicon Oxynitride MCM-41 with High Nitrogen Content

Mesoporous silicon oxynitrides MCM-41 were synthesized successfully. The resulting materials not only have high nitrogen contents and good structural characteristics of MCM-41 (high surface area, narrow pore size distribution and good order), but also are amorphous. The composition and structure of the materials were investigated by CNH element analysis, XPS, Si MAS NMR, XRD, HRTEM and N-2 sorption, respectively. Mesoporous silicon oxynitrides MCM-41 with a high nitrogen content are still non-crystal (amorphous).

Determination of the Insoluble Aluminum Content in Steel Samples by Using Laser-Induced Breakdown Spectroscopy

The insoluble aluminum content in steel samples has a significant influence on the quality of the steel. In this paper, laser-induced breakdown spectroscopy （LIBS） is used to analyze the insoluble aluminum content in steel samples using a scanning mode. The average intensity plus 2.5 standard deviations was iterated and the final iteration value was taken as the threshold that distinguishes soluble and insoluble aluminum, and thus total and soluble aluminum content calibration curves were generated. Using the relevant total and soluble aluminum content calibration curves, the total and soluble aluminum contents in steel samples could be determined. The insoluble aluminum content could be determined by subtracting the soluble aluminum content from the total aluminum content. The insoluble aluminum content of standard samples and process product samples were determined using the present mathematical model; the results agreed well with the certified reference values. This method could be used to rapidly characterize the insoluble aluminum content in steel samples.

Factors Influencing Droplet Size of Silicone Oil Emulsion with High Solid Content

A silicone oil emulsion with 60% of solid content was prepared with methyl silicone oil used as the main material by means of the emulsifier-in-oil method.The influence of emulsification conditions on the droplet diameter of silicone oil emulsion was discussed.The experimental results showed that the emulsification method,including the quantity of the emulsifier,the time and temperature of emulsification,the emulsifying water dosage,and the stirring speed,had significant impact on the droplet size.The optimal conditions were identified to achieve a smallest droplet diameter of the emulsion at an emulsifier dosage of 6%,an emulsification temperature of 70 ℃,an emulsification time of 30 min,and a stirring speed of 1100 r/min,with water added in two portions at a ratio of 1:1.The high-solid content silicone oil emulsion with a mean droplet diameter of 2.731 μm was prepared under these conditions that could ensure absence of stratification and floating oil under centrifuging at a speed of 3000 r/min for 30 min.

Dissection of QTLs for Hull Silicon Content on the Short Arm of Rice Chromosome 6

The QTL qHUS6 for hull silicon content in rice was previously located on the short arm of rice chromosome 6. By using an F2：3 population segregating in the RM587-RM19784 region harboring qHUS6 in an isogenic background, two QTLs for hull silicon content were detected, of which qHUS6-1 was located in the distal region and qHUS6.2 in the region proximal to the centromere. Three rice plants carrying small heterozygous segments in the target region were selected, of which two covered the qHUS6-1 region and the other covered the qHUS6-2 region. Three F2：3 populations were derived from the selfed seeds of the three plants, respectively. QTL mapping was performed using the two populations segregating in the qHUS6-1 region, and qHUS6-1 was delimited to a 147.0-kb region flanked by the markers RM510 and RM19417. Five groups of F3 lines with different genotypic compositions in the qHUS6-2 region were selected from the other F2-3 population. Two QTLs were separated with two-way ANOVA, of which qHUS6-2a was located in the interval defined by RM19706-RM19795 and qHUS6-2b in the interval RM314-RM19665.