Influence Of Si Content Research Articles

Influence of Si Content on Tensile Properties and Fractography of Al-Mg-Si Ternary Alloys.

This study investigated the heat treatment response and tensile properties of Al-6 mass%Mg-xSi (x = 1, 3, 5, and 7 mass%) ternary alloys. Further, the fracture behavior of these alloys in response to heat treatment for different temper conditions was also examined. Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) analysis of the as-cast alloys revealed, in all of them, the presence of iron-bearing phases (in a size range of 10˜60 μm) that did not dissolve or become refined upon heat treatment. Additionally, eutectic Mg₂Si and Al₃Mg₂ phases were found in Alloy I (Al-6Mg-1Si), while eutectic Mg₂Si and Si phases were found in the rest of the alloys. In the as-cast condition, the tensile properties of the examined alloys decreased in relation to increasing Si content. Nonetheless, after heat treatment, the yield strength of the alloys with high Si content (>3 mass%) increased significantly compared with that in the as-cast condition. A yield strength greater than 300 MPa was achieved in both Alloy III (Al-6Mg-5Si) and Alloy IV (Al-6Mg-7Si), although this was achieved at the expense of ductility. According to the fractography of the tensile-fractured surfaces undertaken using optical and scanning electron microscopy, fractures of the iron-bearing phases were found to be the source of cracking in alloys with high Si content. In the case of those with low Si content (≤3 mass%), cracks were believed to have been caused by the debonding of iron-bearing phases from the aluminum matrix.

Influence of Si Content on Fatigue Life for Heat Treated Cast Al-Si-mg Alloy Using Different Quenching Technique

Al-Si-Mg aluminum alloy samples were subjected to solution heat treatment at the temperature of 520 °C for 2 h to attain T42 condition. The heat-treated samples were quenched further in air and water mediums. After quenching, the fatigue life was analyzed with the total strain amplitude (TSA) of 0.4% at the cyclic frequency of 0.3 Hz using a low cycle fatigue testing machine. Air quenched sample has higher life with 1286 cycles than heat-treated and water quenched sample, which were having a fatigue life of 836 cycles and 708 cycles. Tensile mean stress was observed in all samples due to residual stress. Due to fatigue striation, ripple formation was observed in the air quenched sample, and the ripple having the size of 2-3 μm observed under SEM fractography. XRD peaks of Mg2Si and Al3Fe precipitates confirm the proper dispersion during the solution heat treatment.

Nanofriction behaviors between silicon-doped diamond-like carbon films under different testing conditions

Influence of Si contents on nanofriction behaviors between two Si-doped diamond-like carbon (Si-DLC) films is investigated via molecular dynamics simulation. The Si doping induces the friction of these films based on two reasons. The first reason is that the Si doping causes the formation of C-Si bonds in the films and decreases their internal friction, resulting in weak resistances for the relative sliding between them. The other is that the increase in Si content leads to an increase in the proportion of sp3-C atoms but makes them easier to transit to sp2 bonding states, raising the graphitization degree of the films. With high velocities and loads, the friction reductions of these films are also attributed to friction temperatures. A high friction temperature degrades the mechanical strength of the films and enhances their thermal expansions and their graphitization degree, leading to the easy-shear properties of friction interfaces.

Characteristic studies on the ZrCuAlSi multi-component thin-film metallic glasses fabricated by pulsed laser deposition

(Zr47Cu44Al9)100−xSix (x = 0, 0.5, 1.5 and 2.5 at%) thin-film metallic glasses (TFMGs) were deposited at glass substrate by pulsed laser deposition. The influence of Si content and substrate temperature on the microstructure, optical and electrical properties was investigated. After adding Si in the Zr47Cu44Al9 system, the transmittance of the films enhances obviously, especially in the near-infrared region. The resistivity increases and becomes more sensitive to the temperature due to Si addition. With increasing substrate temperatures from room temperature to 430 °C, (Zr47Cu44Al9)98.5Si1.5 films display fully amorphous structure. Appropriate substrate temperature drastically decreases the resistivity of films without degrading the transmittance. (Zr47Cu44Al9)98.5Si1.5 TFMG deposited at 330 °C exhibits the visible transmittance of 49.38%, the infrared transmittance of 80.27% and the resistivity of 7.62 mΩ cm, which are useful properties for their potential applications in infrared technology with the high requirement of radiation resistance and corrosion resistance.

Influence of Si content on the mechanical and wear behavior of Al-xSi-0.4Mg-10Fly ash metal matrix composite

The present work deals with the fabrication of composite by varying the silicon weight percentage and keeping the fly ash constant at 10 wt% to obtain hypoeutectic, eutectic and hypereutectic aluminium metal matrix composite. The microstructure, worn out surface and change in morphology of the developed composite were studied by using a scanning electron microscope. In addition to this, the hardness and tensile properties of the developed composites were discussed. It is observed from the present study that the hardness and tensile values of the composite increases with an increase in wt. % Si. The wear rate of the different composites was determined by pin-on-disk wear testing apparatus and the corresponding wear rate was calculated by varying the different wear testing parameters. It is observed from the wear results that the wear rate of the developed composites decreases as the sliding velocity increases and the wear rate increases with an increase in the applied load.

Thermal expansion behavior of Al–xSi alloys fabricated using selective laser melting

Al–Si alloys are lightweight materials and show excellent mechanical and physical properties, making them appealing for automotive and aerospace industries applications. In this study, Al–(12–50 wt.%)Si alloys (nearly eutectic to hyper-eutectic compositions) were fabricated using a laser-based powder bed fusion process (LPBF) or selective laser melting technique (SLM). The microstructural evolution of the SLM Al–Si alloys as a function of increasing Si contents is investigated in detail. Refined Al and Si phases are observed and the mechanism of the refinement is discussed. In addition, the mechanical properties of the Al–Si alloy processed by casting and SLM were compared. Moreover, the influence of Si content and heating time on the coefficient of thermal expansion (CTE) of the alloys are investigated in detail, and their relationship between theoretical models and the experimental CTE values for the Al–Si alloys will be discussed and compared.

Thermomechanical Fatigue Behavior of Spray-Deposited SiCp/Al-Si Composite Applied in the High-Speed Railway Brake Disc

The thermomechanical fatigue (TMF) behaviors of spray-deposited SiCp-reinforced Al-Si alloy were investigated in terms of the size of Si particles and the Si content. Thermomechanical fatigue experiments were conducted in the temperature range of 150-400°C. The cyclic response behavior indicated that the continuous cyclic softening was exhibited for all materials, and the increase in SiC particles size and Si content aggravated the softening degree, which was attributed to dislocation generation due to differential thermal contraction at the Al matrix/Si phase interface or Al matrix/SiC particle interface. Meanwhile, the TMF life and stress amplitude of SiCp/Al-7Si composites were greater than those of Al-7Si alloy, and increased with the increasing SiC particle size, which was associated with “load sharing” of the direct strengthening mechanism. The stress amplitude of 4.5μmSiCp/Al-Si composite increased as the Si content increased; however, the influence of Si content on the TMF life was not so significant. The TMF failure mechanism revealed that the crack mainly initiated at the agglomeration of small-particulate SiC and the breakage of large-particulate SiC, and the broken primary Si and the exfoliated eutectic Si accelerated the crack propagation.

Influence of Si Content on Properties of Ti(1-x)SixN Coatings

To investigate the evolution of microstructure and wear behavior of TiSiN coatings with the variation of Si in targets and lays the foundation for its controllable mass production, Ti(1-x)SixN composite coatings were deposited onto Si (100) and cemented carbide substrates using TiSi targets with different Si content by cathodic arc ion plating. The influences of Si on the microstructure and mechanical properties were studied. Nano-amorphous composite structure appeared in the Ti(1-x)SixN coatings when Si content in TiSi target was higher than 5at%. However, further increase of Si content in TiSi target exhibited a negligible effect on the microstructure of Ti(1-x)SixN coatings. Hardness and deformation resistance were correlated to the content of Si in TiSi targets. Maximum hardness was obtained as the Si content in target increased up to 20at%. Friction coefficient and wear rate significantly decreased with addition of Si in TiN coating, and then dually increased with the increase of Si content in targets.

Ab initio Insight Into the Structure and Properties of Zr–Si System

A first‐principles investigation on the electronic structure, mechanical, and thermal properties of Zr–Si compounds has been investigated to prompt the development of new materials. The influence of Si content on mechanical and thermal properties is clarified. All the Zr–Si compounds are strikingly incompressible under uniaxial stress along x, y, and z axes. β‐ZrSi possesses the strongest resistance to shape change and uniaxial tensions. α‐ZrSi presents better performance of the resistance to volume change. The bulk modulus first increases and then decreases with the increase of the Si concentration. All the compounds exhibit brittle behavior. These zirconium silicides have relatively low bulk and shear modulus, but the shear anisotropy is strongly dependent on diverse directions. Debye temperature increases linearly with the increase of Si content. ZrSi2 shows the best capacity of thermal conductivity. The minimum thermal conductivity in all the crystallographic directions is progressively increased with the increase of Si content except for β‐ZrSi in the [010] direction.

On the Impact of Si Content and Porosity Artifacts on the Anodizing Behavior of Additive Manufactured Al-Si Alloys

This work analyzes the galvanostatic anodizing behavior of additive manufactured (AM) Al-Si alloys. Two main factors were studied here: 1) the influence of Si content on the anodizing behavior and on the porous structure of the anodic oxide film, and 2) the effect of pre-existing internal pores on the anodizing behavior of these materials. Three different alloys were anodized in H2SO4 electrolyte, with 7%, 10%, and 12% Si. The voltage responses of the different samples during anodizing were compared and the formed oxide was analyzed. The amount of Si in the AM Al-Si alloys was found to have a great influence on the anodizing voltage and consequently on the porous structure of the anodic oxide layer. However, the anodic oxide growth rate was nearly independent of the Si content in the samples. Moreover, the effect of internal porosity resulting from the metal additive manufacturing process on the anodizing behavior of these specimens was also analyzed. An outer anodic oxide layer decorated the pre-existing internal pores that were reached by the anodic oxide front. These internal pores were also characterized by the systematic appearance of cracks resulting from the volume expansion of anodic oxide layers advancing in opposite directions.

Investigation of Si content on the grain refinement of Al-Si alloy under pulsed magnetic field

The influence of Si content and pulsed magnetic filed parameters on the solidification structure of the Al-Si binary alloy was investigated. Experimental results indicated that the addition of Si has a significant refinement on the macrostructure of the commercial pure aluminum. The grain size of the Al-Si binary alloy decreases first and then increases with increasing of Si content which could be caused by the constitutional-supercooling, but for the case where a PMF was applied, the grain size was further refined compared with as-cast state.

Fabrication of Al–Si Gasar by mold casting technique

AbstractAl–Si Gasar were produced using the metal–gas eutectic process. Directionally solidified porous Al–Si alloys with varying Si content were prepared by using a mold casting technique under different values of hydrogen saturation pressure. The influence of Si content on pore formation was studied; specifically, shape, size, porosity, circularity, and distribution along the height of the specimen were investigated. We observed that at increased levels of Si content, pores become more spherical and larger in diameter, while porosity decreases. Specimens produced by using different casting techniques exhibit differences in porosity, pore shape, and the relationship between porosity and the alloys’ Si content. Compression tests were performed to compare the mechanical properties of bulk alloys with porous, Gasar alloys.

The influence of silicon additions on the deformation behavior of austenite-ferrite duplex medium manganese steels

The present study systematically investigated the effect of Si additions from 0 to 3 wt.% on the deformation mechanisms of a 0.2C-10Mn-3Al medium Mn steel. Two austenite-ferrite duplex microstructures, characterized by the different austenite characteristics (i.e. fraction and stability), were produced for different Si-alloyed steels by intercritical annealing and subsequently subjected to tensile testing. The influence of Si content on the activation and kinetics of transformation-induced plasticity (TRIP) effect, the formation of deformation twins, as well as the strain partitioning between phase constituents during deformation was studied in detail. For the low austenite fraction (∼30%) duplex structure with a high austenite stability (low Ms temperature), the tensile strength was only slightly changed with Si levels, whereas the uniform elongation was significantly influenced, with first an increase followed by a decreasing trend with higher Si contents. This was attributed to changes in strain partitioning between austenite and ferrite and to different extent of deformation twinning in austenite, which were highly dependent on the solute Si contents and the related microstructural changes. It was found that strain partitioning in this type of microstructure can result in a substantially high strain hardening rate and high uniform elongation. Conversely, for the samples with a high austenite fraction (∼45%) and low stability, the tensile properties were insensitive to the Si content, being mainly controlled by the TRIP effect. In this structure, a higher fraction of martensite was formed at the beginning of the plastic deformation, which decreased the strain partitioning between austenite and ferrite. The TRIP effect after the Lüders strain is believed to be the main factor influencing the strain hardening rate of this type of structure.

Influence of Si Content on the Microstructure and Corrosion Behavior of Additive Manufactured Al-Si Alloys

This work evaluates the corrosion resistance of three Al-Si alloys processed by additive manufacturing (Al-Si7-Mg, Al-Si10-Mg, and Al-Si12) through a comparative analysis. It explores the influence of the silicon content on the microstructure and corrosion behavior of these alloys. An initial scanning electron microscopy analysis revealed that the silicon content in the samples affected the level of connectivity of the Si network, and this, consequently, influenced the formation of micro-cracks during corrosion. A model describing the evolution of the corrosion attacks and micro-cracks formation in the AM Al-Si alloys is proposed here.

Microstructure and mechanical properties of magnetron sputtered Ti-Si-N coatings with different silicon content

This work deals with the deposition and characterization of (Ti-Si-N) coatings. A series of Ti-Si-N thin films with different silicon content were deposited on Si (100) substrate by RF magnetron sputtering in an Ar-N2 gas mixture. The influence of Si content on the microstructural and mechanical properties of the as deposited. The as deposited films were studied by using different characterization techniques such as SEM equipped with Energy Dispersive X-ray spectroscopy (EDS) for determining the composition of the films, XRD was used to determine microstructural composition and nano-indentation with MTS XP system for mechanical properties. Scherer’s formula was used to determine the grain size, from the full width at half maximum of (111) experimental peaks, residual stresses of the films were measured by an optical interference apparatus using Newton’s ring method            Results reveal that the film deposited with Si content of 20 at. % has a dense nanostructure and the surface morphology of the Ti-Si-N coatings show neither holes nor column headings. The film deposited with Si content of 33 at. % shows a surface morphology of damaged surface. The X-ray spectra show that Ti-Si-N coatings deposited with Si content of 0 at.%, 27 at.%, 33 at.%, 40 at.% possess a preferential orientation in the direction of (111) and this orientation peak disappears for films with low of Si content. The residual stress built in the coating is compressive and they increase with increase in Si content and reach a maximum of 2.22 GPa. The hardness of the Ti-Si-N films also increases to a maximum with increase in Si content beyond which further addition of the Si decrease the hardness. The TiN grain size as calculated from the XRD diffraction peak decreases with increase in the Si content to saturation value of around 12.8nm for films without addition of silicon to 3.8nm for films with 40at. % of Si   Keywords:   hard coating, magnetron sputtering, residual stress; grain size, Ti-Si-N

Influence of Si content on the wettability and corrosion resistance of nanocomposite TiSiN films deposited by pulsed-DC PACVD

In this paper, in order to improve the wettability and corrosion resistance of Ti-6Al-4V, titanium silicon nitride (TiSiN) films with different Si contents were deposited on this alloy using pulsed-DC plasma-assisted chemical vapor deposition (PACVD) method. The results indicated that the TiSiN films have a nanocomposite microstructure in which the TiN nanocrystallines are surrounded by an amorphous matrix of SiNx. With increasing Si content from 0 to 24.7 wt%, the film's water contact angle reduced from 82.2° to 47.5° due to the formation of a hybrid TiO2/SiO2 surface oxide layer on the TiSiN film and also rising its surface roughness from 21 to 32 nm. The electrochemical studies in a simulated body fluid (SBF) at 37 °C showed that the TiSiN films due to the nanocomposite microstructure, formation of a hybrid SiO2/TiO2 passive oxide layer and lower microstructural defects in comparison with TiN film can act as a more effective protective barrier layer against the corrosive liquid. In the electrochemical impedance spectroscopy (EIS) examinations, the TiSiN film with 12.1 wt% of Si represented the best corrosion resistance compared to the uncoated Ti-6Al-4V alloy and the other TiSiN films with 0, 6.3, 17.8 and 24.7 wt% of Si.

Influence of Si content on mechanical and tribological properties of TiAlSiN PVD coatings at elevated temperatures

TiN- and CrN-based binary or ternary coatings have been used for many years in order to extend the service life of machining tools. The increasing demands in the metalworking industry require more efficient coating systems. According to recent studies, silicon offers promising opportunities to positively influence the characteristics of thin titanium or chromium-based coatings. The nanocomposite TiAlSiN presents a high hardness and a fine grain structure. Furthermore, by adding silicon, the oxidation resistance as well as the tribological properties can be increased and improved.In this study, TiAlSiN coatings with different Si contents (0–10.9at%) were produced by means of magnetron sputtering. In order to test the possibility to sputter pure, low conductive silicon targets, different sputter and bias modes were tested. The ratios of the other coating elements were kept constant while varying the silicon content inside the PVD coatings. Nitrided steel samples (AISI H11) were used as substrate materials. The influence of the Si content on the tribomechanical properties of TiAlSiN were analyzed. The analyses focused on the coatings with a silicon content of 5–10at% due to the change of the coating morphology within this range. The coating morphology and different chemical compositions of the silicon-doped coatings were investigated by means of scanning electron microscopy and EDX analyses. Phase analyses were conducted and residual stresses were measured by means of X-ray diffraction. The hardness and Young's modulus of the PVD coatings were investigated using nanoindentation. Furthermore, scratch tests were performed in order to characterize the adhesion between the substrate and the coating. Finally, high temperature tribometer tests were executed to determine the wear resistance of the TiAlSiN coatings at room temperature as well as at elevated temperatures (500°C, 800°C).

Influence of Si content on the microstructure and mechanical properties of VSiN films deposited by reactive magnetron sputtering

A series of VSiN composite films with different Si content were deposited at room temperature by reactive magnetron sputtering. XPS, XRD, SEM, SAED, HRTEM, 3D Profilometer and Nano-indentation were employed to characterize the composition, microstructure, cross-sectional morphology and mechanical properties of the films. The results reveal that the c-VN phase and t-V5N phase coexist in films with different Si content and the c-VN is the major phase. The substitutional solid solution of (V,Si)N is formed when the Si content is less than 1.3 at.%. With a further increase of Si content, excess Si are aggregated in the grain boundary and amorphous Si3N4 is formed. It was found that minute traces of Si atoms can promote the growth of grain. A two-dimensional model was built in this study to reveal the existing forms of Si element and its influence on the microstructure and mechanical properties of VSiN films at different stages of the modelling process.

Effects of Si Content and Aging Temperature on Wear Resistance of Surfacing Layers Welded with 4043 Aluminum Welding Wires

Abstract 4043 aluminum welding wires are extensively used for welding 6000 series aluminum alloys due to the good flow ability of the fusion state and the low cracking tendency during welding process. Some scratches and wear on the surfaces of aluminum structural components can be repaired by surface welding with 4043 aluminum welding wires. In the present study, the influences of Si content and aging temperature on the wear resistance property of the surfacing layers welded by tungsten inert gas (TIG) welding using 4043 aluminum welding wires have been analyzed by optical microscopy, scanning electron microscopy, hardness testing and abrasive wear testing. The results show that the increase in Si content can increase the fraction of eutectic Si particles, and the heat treatment can spheroidize eutectic Si particles, resulting in further improving the wear resistance property of the surfacing layers.

Influences of Silicon on Properties of Hard Drawn Aluminium Wire

Influences of Si content on the tensile strength and electrical resistivity of hard drawn aluminium wire were studied in this paper. It showed that the electrical resistivity and tensile strength of the wire improved with the increase of Si content, and trace content of Si led to significant increase of the electrical resistivity. It was analyzed that Fe dissolved in the α(Al) matrix in form of supersaturated solid solution and its solid solubility was about 0.03%. Similarly Si dissolved in α(Al) in form of solid solution when its content was low, and with the content increased to certain content, redundant Si would precipitate as secondary phase transforming from AlFe binary compound to AlFeSi ternary intermetallic compound of α(Al 12 Fe 3 Si 2 ) then β(Al 9 Fe 2 Si 2 ) phase.