Decrease Of Si Content Research Articles

Roles of Silicon Content and Normalization Temperature on Cold Workability and Recrystallization of High-Grade Non-Oriented Silicon Steel

In order to decrease the difficulty of cold workability and study the recrystallization behavior of high-grade non-oriented silicon steel, Si content and normalization temperature were optimized simultaneously. The microstructure and texture of both hot-rolled sheet and normalized annealing sheet presented a gradient distribution. With the decrease in Si content from 3.02% to 2.54% and increase in normalization temperature from 850 °C to 920 °C, Goss texture ({110}<001>) intensity at surface layer and α-fiber (<110>//RD) texture intensity were strengthened, and α-fiber texture gradually turned to α*-fiber ({1 1 h}<1/h 1 2>) in the normalized annealing sheet. Recrystallization ratio and recrystallization grain size were increased both in the hot-rolled sheet and the normalized annealing sheet. The tensile strength and yield strength of normalized annealing sheet were reduced by 65 Mpa, which decreased the cold workability difficulty and improved cold rolling yield. The cold rolled microstructure had wider shear bands which nucleated earlier but recrystallized velocity was slower because of lower cold rolled energy storage during interval recrystallization annealing, resulting in a more heterogeneous grain size distribution in the final annealing sheet.

Developing Al–Fe–Si alloys with high thermal stability through tuning Fe, Si contents and cooling rates

The use of recycled aluminum alloys can greatly reduce energy consumption and carbon emissions, but the high iron content limits the scope of application of recycled aluminum alloys. The development of alloys with good performance under high Fe content can enable iron-rich recycled aluminum alloys to have a new application direction. The key is to control the type and morphology of the Fe-rich phase in the alloy. In this work, the microstructure evolution of Al–Fe–Si alloys with varying Fe, Si contents and cooling rates was studied. It is found that as the Si content decreases, the iron-rich phases transform from the β-Al9Fe2Si2 to the eutectic α-Al8Fe2Si. Within a certain composition range, increasing the cooling rate will not only refine the microstructure but also promote the transformation of β-Al9Fe2Si2 to α-Al8Fe2Si. In this study, a microstructure containing only one type of second phase, in the form of fine eutectic α-Al8Fe2Si, has been obtained by water cooling of Al–5Fe–3Si melt. The mechanical properties of the alloy are similar to those of the Al–Si alloy under the same conditions, while the thermal stability of the microstructure is significantly better than that of the Al–Si alloy. These findings not only provide new insights for avoiding β-Al9Fe2Si2 phase in aluminum alloys, but also provide guidance for the development heat-resistant alloys with Al - α-Al8Fe2Si eutectic structures.

Enhancement of thermal and mechanical stabilities of silicon doped titanium nitride coating by manipulation of sputtering conditions

This study investigates the influence of substrate (AISI M42 tool steel) bias voltage (from −30 to −80 V), on the mechanical properties of magnetron sputtered TiSiN coating derived from Ti and Si targets. Thermal stability, microstructure (crystallite size, microstrain, lattice constant), morphology and mechanical (hardness, Young's modulus, residual stresses) properties, of the deposited TiSiN coatings, were investigated with synchrotron powered X-ray diffraction (SR-XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and nanoindentation techniques. Rietveld analysis, of the in-situ SR-XRD, in the temperature range of 25–800 °C, demonstrated cubic TiN form in (Ti,Si)N solid solutions, with TiO2 and Ti2O3 identified at lower bias voltages. Density functional theory supplemented the experimental results.Increase in the bias voltage resulted in: (i) a decrease in Si content, (ii) significant smoothening of surface morphology, (iii) change in the phase composition and microstructure, (iv) improved oxidation resistance and thermal oxidation threshold, and (v) hardness and Young's modulus of the coatings increased up to 50% to 33 GPa and 450 GPa, respectively.

Effects of Al, Si and N Content on the Formation of M-A Constituent and HAZ Toughness of Ti-Containing Low-Carbon Steel

The present work investigated the effects of Al, Si, and N content on the impact toughness of the coarse-grained heat-affected zone (CGHAZ) of Ti-containing low-carbon steel. Simulated CGHAZ of differing Al, Si, and N contents were prepared, and Charpy impact toughness was determined. The results were interpreted in terms of microstructure, especially martensite-austenite (M-A) constituent. All elements accelerated ferrite transformation in CGHAZ but at the same time increased the amount of M-A constituent, thereby deteriorating CGHAZ toughness. It is believed that Al, Si, and free N that is uncombined with Ti retard the decomposition of austenite into pearlite and increase the carbon content in the last transforming austenite, thus increasing the amount of M-A constituent. Regardless of the amount of ferrite in CGHAZ, its toughness decreased linearly with an increase of M-A constituent in this experiment, indicating that HAZ toughness is predominantly affected by the presence of M-A constituent. When a comparison of the effectiveness is made between Al and Si, it showed that a decrease in Si content is more effective in reducing M-A constituents.

A review on transfer mechanism and influence factors of silicon in blast furnace

ABSTRACTThe Si content in pig iron is one of the important indicators for evaluating the technical level of ironmaking in the blast furnace. From the late twentieth century, the production of low-Si pig iron has attracted more and more attention in steel industries of the world. For ironmaking process, the decrease of Si content is beneficial for increasing the coefficient of utilization of the capacity of blast furnace, reducing the fuel consumption and increasing the output. For the following steelmaking process, the decrease of Si content is beneficial for reducing the amount of slag, consumption of flux and shortening steelmaking time. Overall, it is an important technology for productivity enhancement and energy saving. In this paper, the transfer mechanism and influence factors of Si in blast furnace have been reviewed and discussed in detail. This paper will provide theoretical basis and operation strategies for reducing the Si content.

Effect of Si content on microstructure and cryogenic toughness of heat affected zone of low nickel steel

Compared with 9%Ni steel, low nickel steel has great advantages in cost and weldability. However, cryogenic toughness of the heat affected zone (HAZ) of conventional low nickel steel deteriorates, which limits its application in the construction of liquefied natural gas tanks. In this work, two low nickel steels with different Si contents were designed, and the relationship between Si content and HAZ cryogenic toughness of these steel samples was investigated. After reducing Si content, the required Charpy impact absorbed energy was obtained in the HAZ at fusion line and 1 mm from fusion line. Microstructural characterization revealed that the reduction in Si content promoted auto-tempering of coarse-grained HAZ (CGHAZ), leading to improved plastic deformation ability of the matrix. In intercritically reheated CGHAZ (ICCGHAZ), martensite-austenite (M-A) constituents were formed, which consisted of twin martensite and austenite. The decrease in Si content reduced the amount and size of M-A constituents and changed their elongated morphology to blocky morphology, which is also believed to be beneficial for ICCGHAZ cryogenic toughness. This work provides a novel way to soften the HAZ microstructure for improving its cryogenic toughness.

Effect of dwelling time in VIM furnace on chemical composition and mechanical properties of a Ni–Fe–Cr alloy

The mechanical properties and changes in chemical compositions and microstructure of a Ni–Fe–Cr alloy in different dwelling time in a vacuum induction melting (VIM) furnace were studied. The chemical analysis shows that the dissipations of Al, Ti and Si increase with increasing the dwelling time in the VIM furnace. With the decrease in Si content due to increasing the dwelling time in the VIM furnace, the segregation of niobium is reduced, resulting in lower incoherent δ phase in the grain boundaries. This incoherent δ phase promotes intergranular fracture in the specimen with the lowest dwelling time. The dissipations of Al and Ti with increasing the dwelling time in the VIM furnace lead to decrease the hardness, yield and ultimate tensile strengths of the alloy, while the elongation increases owing to the lower number of inclusions and strengthening phase (γ″).

Arsenite phytoextraction and its influence on selected nutritional elements in one-year-old tree species

Trees have long been recognized as promising for arsenic phytoremediation, however, the most suitable traits of various tree species are still under examination. Therefore, the aim of the studies was to investigate the uptake and accumulation capabilities of As(III) by one-year-old trees from of species (Acer platanoides L., Betula pendula Roth., Quercus robur L., Ulmus laevis Pall) using hydroponic culture. A further aim was to analyse the influence of As(III) on the content of selected nutritional minerals, such as B, Ca, K, Mg, Na and Si.The highest accumulation of As(III) was detected in A. platanoides (BCF=2.16) and Q. robur (BCF=2.69). In A. platanoides >80% of total As(III) of the whole plant was accumulated in its stem while its TF was 10.8. Q. robur TF was 0.1 and it accumulated As(III) predominantly in its roots – >85% of total As(III) of whole the plant. The high As(III) accumulation capabilities of A. platanoides and its location predominantly in the stem classify this tree species as a hyperaccumulator and a good candidate for As(III) phytoextraction while Q. robur would be more suitable for phytostabilization and eco-restoration.As(III) uptake also caused alteration in the content of nutritional minerals. Decreased levels of B and Si were detected in the roots of most trees exposed to As(III) indicating the competition between these elements in the uptake process. In A. platanoides stems a high accumulation of As(III) resulted in a significant decrease of Si content in all the studied organs, suggesting that As(III) was transported from root to shoot predominantly by Si transporters.As(III) also led to a general alteration in the level of other macronutrients – e.g. an increase in the level of Na and K. The reactions varied between tree species and organs. Hence, As(III) uptake and accumulation results in a deterioration of cation balance and homeostasis, which could be one of the factors affecting the vitality of the examined trees.

Si/SiC optical coatings for C/SiC composites via gel-casting and gas silicon infiltration: Effects of carbon black content

The dense Si/SiC coatings are fabricated by means of gel-casting (GC) and gas silicon infiltration (GSI) for the first time, using carbon black and α-SiC as raw materials. The influences of the carbon black content on the properties of the coating samples have been investigated. Results show that, with the increase of the carbon black content, the viscosity of the slurry increase dramatically, the density and the porosity are closer to theoretical results, leading to the higher density after GSI. And the β-SiC content increases as well as the Si content decreases, resulting in the increase of the mechanical and the thermal matching properties. It is also worth noting that the roughness of the coating of φ160 mm comes to 0.57 nm after polished. The study highlights that the combined application of the GC and the GSI processes can produce high-quality Si/SiC coatings that are suitable in the space optical applications.

Developing methodologies for source attribution: glass phase separation in Trinitite using NF3

Abstract This study details thermal reactions between glasses, common minerals, and Trinitite post-detonation material with the fluorinating agent nitrogen trifluoride (NF3). The ultimate goal of our investigation is to develop a relatively rapid method for the effective separation of bomb components from complex matrices resulting from a nuclear explosion. Trinitite samples, silicate minerals (quartz; plagioclase and microcline), amorphous SiO2, calcite, a natural glass (obsidian), and two synthetic glasses were characterized extensively before and after the fluorination to fully understand the effects of the NF3 thermal treatment. Samples were reacted with NF3 using a combined thermogravimetric (TG) differential thermal analysis (DTA) unit, as well as in a stainless steel bomb reactor connected to a fluorination line. Subsequent to the NF3 treatment, samples were imaged by scanning electron microscopy in order to document changes in grain size and morphology. Energy dispersive spectroscopy was performed to determine changes in major element abundances. Results demonstrate that rates of reaction are dependent on grain size, temperature, pressure, and time of fluorination. All mineral samples experienced mass loss during fluorination. Specifically, amorphous SiO2 (~90% mass loss) experienced the most while calcite experienced the least (~18%). Major element analysis reveals that mass loss is attributable to the volatilization of silica (SiO2) in Si-bearing phases, or sample decomposition in calcite due to fluorination. Results for fluorinated samples of Trinitite demonstrate that mass loss occurs at different rates for each sample, but each sample experienced an expected large decrease in Si content (resulting from volatilization of SiF4). Hence, the concentration of metals in the residual material increased due to the volatilization of Si. These results validate that this thermal-fluorination technique allows the separation of silica from minerals (i.e. naturally occurring crystalline materials) and glasses (i.e. amorphous materials), leaving behind non-volatile fluorinated species and refractory phases. The results from our investigation clearly indicate that the NF3 treatment of nuclear materials is a technique that provides effective separation of bomb components from complex matrices (e.g. post-detonation samples), which will aid with rapid and accurate source attribution.

Influence of Ti and La Additions on the Formation of Intermetallic Compounds in the Al-Zn-Si Bath

The effect of Ti and La additions on the formation of intermetallic compounds (IMCs) in the galvalume (55Al-Zn-1.6Si wt pct) bath was investigated experimentally and further studied with first-principles calculation. The studied baths contain: 1 wt pct Fe, with Ti content ranging from 0.05 to 0.15 wt pct and La content ranging from 0.05 to 0.30 wt pct. Combination of the experimental results with the thermodynamic analysis shows that the solubility of Fe in the alloy bath decreases with an increase of Ti content, which results in the formation of mass dross. Compared with the Ti-containing alloy, La promotes the formation of τ 5 phase (Fe2Al8Si). When both Ti and La are added, Fe4Al13, τ 5, τ 6 (β-Al4.5FeSi), TiAl3, and Ti2Al20La phases were observed. Since these IMCs would consume more Si in the bath, the decrease of Si content with Ti and La additions is more significant than that of the bath without these additions. Furthermore, the formation mechanism of Ti/TiAl3/Ti2La20La core–shell structure in the coating bath is proposed. This study has implications for strategic design of industry hot-dip production with exceptional mechanical properties of Al alloy coating.

Research on Elements Distribution in Hot Dip Aluminum Silicon Coating of Hot Stamping Steel

Al-Si coating in different hot dip process conditions were made by a hot-dip galvanizing simulator, and distribution regularities of chemical elements in coating were studied by means of GDS, SEM, EDS and XRD. The results show that the hot dip temperature has no obvious impact on elements distribution in coating, but has some impact on Si content in surface coating. The hot dip time has no obvious impact on surface coating element content, but has distinct impact on deep coating element content. With the hot dip time increasing, Al content decreases, Fe content increases, and Si content decreases. Al-Si coating is composed of 3 layers, surface layer contains fine and close Al2O3 film, which has good anti-oxidation property on high temperature and hot stamping property, middle layer contains high melting point phase ,such as rich Fe phase , FeAl3 ,which has excellent anti-oxidation property on high temperature. The elements in diffusion layer can even be transited to basic steel, so coating has good adhesion property.

Effect of Si content on microstructure and properties of Si/Al composites

Si/Al composites with different Si contents for electronic packaging were prepared by spark plasma sintering (SPS) technique. Properties of the composites were investigated, including density, thermal conductivity, coefficient of thermal expansion and flexural strength. The effects of the Si content on microstructure and thermal and mechanical properties of the composites were studied. The results show that the Si/Al composites consist of Si and Al components and Al uniformly distributes among Si grains. The relative density of the Si/Al composites gradually increases with the decrease of Si content and reaches 98.0% when the Si content is 50%. The thermal conductivity, the coefficient of thermal expansion and the flexural strength of the composite all decrease with the increase of the Si content, and an optimal matching of them is obtained when the Si content is 60% (volume fraction).

Dislocation dynamics in SiGe alloys

The dislocation velocities and mechanical strength of bulk crystals of SixGe1−x alloys grown by the Czochralski method have been investigated by the etch pit technique and compressive deformation tests, respectively. Velocity of dislocations in the SiGe alloys of the composition range 0.004 < x < 0.08 decreases monotonically with an increase in Si content at temperature 450–700°C and under stress 3–24MPa. In contrast, velocity of dislocations in the composition range 0.92 < x < 1 first increases, then decreases and again increases with a decrease in Si content at temperature 750-850°C and under stress 3–30MPa. The velocity of dislocations was quantitatively evaluated as functions of stress and temperature. Stress-strain behaviour in the yield region of the SiGe alloys of composition 0 < x < 0.4 is similar to that of Ge at temperatures lower than about 600°C. However, the yield stress becomes temperature-insensitive at high temperatures and increases with increasing Si content. The stress-strain curves of the SiGe alloys of composition 0.95 < x < 1 are similar to those of pure Si at temperatures 800–1000°C and the yield stress increases with decreasing Si content down to x = 0.95. The yield stress of the SiGe alloys is dependent on the composition, being proportional to x(1−x), showing a maximum around x ≈ 0.5. Built-in stress fields related to local fluctuation of the alloy composition and the dynamic development of a solute atmosphere around the dislocations, may suppress the activities of dislocations and lead to the hardening of SiGe alloys.

Light absorption and electrical transport in Si:O alloys for photovoltaics

Thin films (100–500 nm) of the Si:O alloy have been systematically characterized in the optical absorption and electrical transport behavior, by varying the Si content from 43 up to 100 at. %. Magnetron sputtering or plasma enhanced chemical vapor deposition have been used for the Si:O alloy deposition, followed by annealing up to 1250 °C. Boron implantation (30 keV, 3–30×1014 B/cm2) on selected samples was performed to vary the electrical sheet resistance measured by the four-point collinear probe method. Transmittance and reflectance spectra have been extracted and combined to estimate the absorption spectra and the optical band gap, by means of the Tauc analysis. Raman spectroscopy was also employed to follow the amorphous-crystalline (a-c) transition of the Si domains contained in the Si:O films. The optical absorption and the electrical transport of Si:O films can be continuously and independently modulated by acting on different parameters. The light absorption increases (by one decade) with the Si content in the 43–100 at. % range, determining an optical band gap which can be continuously modulated into the 2.6–1.6 eV range, respectively. The a-c phase transition in Si:O films, causing a significant reduction in the absorption coefficient, occurs at increasing temperatures (from 600 to 1100 °C) as the Si content decreases. The electrical resistivity of Si:O films can be varied among five decades, being essentially dominated by the number of Si grains and by the doping. Si:O alloys with Si content in the 60–90 at. % range (named oxygen rich silicon films), are proved to join an appealing optical gap with a viable conductivity, being a good candidate for increasing the conversion efficiency of thin-film photovoltaic cell.

Preparation of SixCo0.3Cu0.3Cr0.6Al0.2/modified graphite sphere composites and their electrochemical performance as anode materials for Li-ion batteries

Abstract New anode composite materials comprising Co, Cu, Cr, Al and Si in conjunction with graphite for Li-ion batteries are synthesized using high energy ball milling (HEBM) technique. The microstructure and morphology of the ball-milled Si x Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /modified graphite sphere composites (labeled as Si x Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /MGS, x = 1.12, 1.74, 2.84) are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). In addition, X-ray photoelectron spectroscopy (XPS) is used to detect the chemical compositions of Si 2.84 Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 and Si 2.84 Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /MGS surfaces. The electrochemical behaviors of Si x Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /MGS are investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge techniques. With the decrease of Si content, the specific capacity of Si x Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /MGS decreases, but the capacity retention becomes better. Among them, Si 1.74 Co 0.3 Cu 0.3 Cr 0.6 Al 0.2 /MGS presents good cyclic performance with a high reversible capacity (about 600 mA h g −1 ).

Thermodynamic properties and interfacial layer characteristics of HfO2 thin films deposited by plasma-enhanced atomic layer deposition

The thermodynamic properties and interfacial characteristics of HfO2 thin films that were deposited by the direct plasma atomic layer deposition (DPALD) method are investigated. The as-deposited HfO2 films that were deposited by the DPALD method show crystallization of the HfO2 layers, which initiates at approximately the 35th cycle (about 2.8nm) of the DPALD process. Medium-energy ion scattering analysis reveals that the direct O2 plasma causes a compositional change in the interfacial layer as the process progresses. With an increase in the number of process cycles, the Si content decreases and the O content increases at that position, so that the HfO2-like Hf-silicate layer is formed on top of the interfacial layer. The enhanced physical reactivity of the oxygen ions in the direct plasma and the Hf-silicate layer may be the driving forces that accelerate the early crystallization of the HfO2 layer in the DPALD process in the as-deposited state.

Depth redistribution of components of SiO x layers prepared by magnetron sputtering in the process of their decomposition

The process of thermal decomposition of SiO x layers prepared by magnetron co-sputtering of Si and SiO 2 on Si and quartz substrates is studied by Auger and secondary ion mass spectroscopies. It is found that high temperature annealing of the layers causes a Si-depleted region near the layer/substrate interface. It is shown that the formation of this region does not depend on the type of substrate but depends on the content of excess Si and is observed at high content of excess Si. When the excess Si content decreases, the Si-depleted region at first smears and then disappears. The mechanism of SiO x decomposition and possible reasons for the appearance of the Si-depleted region are discussed.

Characterization of nitrogen-rich silicon nitride films grown by the electron cyclotron resonance plasma technique

Amorphous hydrogenated silicon nitride films have been deposited by the electron cyclotron resonance plasma technique, using N2 and SiH4 as precursor gases. The gas flow ratio, deposition temperature and microwave power have been varied in order to study their effect on the properties of the films, which were characterized by Rutherford back-scattering spectrometry, elastic recoil detection analysis (ERDA), Fourier transform infrared spectroscopy and ellipsometry. All samples show N/Si ratios near or above the stoichiometric value (N/Si = 1.33). The hydrogen content determined from ERDA measurements is significantly higher than the amount detected by infrared spectroscopy, evidencing the presence of non-bonded H.As the N2/SiH4 gas flow ratio is increased (by decreasing the SiH4 partial pressure), the Si content decreases and the N–H concentration increases, while the N content remains constant, resulting in an increase of the N/Si ratio. The decrease of the Si content causes a decrease of the refractive index and the density of the film, while the growth ratio also decreases due to the limiting factor of the SiH4 partial pressure. The infrared Si–N stretching band shifts to higher wavenumbers as the N–H concentration increases.The increase of deposition temperature promotes the release of H, resulting in a higher incorporation of N and Si into the film and a decrease of the N/Si ratio. The effect of increasing the microwave power is analogous to increasing the N2/SiH4 ratio, due to the increase in the proportion of nitrogen activated species.

熱間工具鋼の被削性におよぼすＳｉ量の影響

This study has been carried out to clarify the effect of Si content on machinability of 5%Cr-3%Mo type hot working die steel hardened and tempered to 49HRC. The results are as follows. (1) Carbides retained in hardened and tempered specimens are M6C and MC and the amount of these carbides decrease with the decrease in Si content. (2) In end-milling, carbide tools exhibit shorter life with decreasing Si content, especially at the range of Si content less than 0.3%. Adhesive wear increases with the decrease in Si content. (3) In turning by carbide tools, the cutting forces and temperatures rise with decreasing Si content. (4) High speed tensile test at elevated temperatures reveals that the steels with lower Si content show higher maximum flow stress and larger reduction of area. (5) By the calculation of turning-cutting forces based on the two-dimensional cutting model, it is found that the decrease in Si content raises the shear stress resulting in the increase of cutting forces. The high shear stress of lower Si steels is considered due to their high strength at elevated temperature.