Si Ternary System Research Articles

Interdiffusion of Solute Elements in the <i>α</i>-Fe Phase of the Fe–Cr–Mo and Fe–Cr–Si Ternary Systems

Interdiffusion of Solute Elements in the <i>α</i>-Fe Phase of the Fe–Cr–Mo and Fe–Cr–Si Ternary Systems

Synergistic effect mechanism of biomass ash-derived K-Ca-Si catalytic system on syngas production and reactivity characteristics of high-sulfur petroleum coke gasification

In this study, three typical biomass ash (BA) components, KCl, CaCO3 and SiO2, are selected as model compounds to construct BA-based key ternary component system for petroleum coke (PC) gasification. Gas product analysis was conducted using gas chromatography to study the influence of different catalysts on the gas product distribution, gas yield and carbon conversion of PC gasification, and clarify the synergistic effects of binary and ternary components in K-Ca-Si catalytic system. In addition, electron scanning microscopy (SEM) and Raman techniques are used to characterize the physicochemical structure of gasification semi-char to reveal the synergistic mechanism of K-Ca-Si system. The results show that the yield of different gases is ordered as H2 > CO > CO2 and the increment of H2 yield, CO yield, syngas yield and carbon conversion in K-Ca-Si catalytic system is 43.41 mmol/g, 26.67 mmol/g, 80.37 mmol/g and 0.49, compared with single PC gasification, respectively. By comparing the theoretical and actual value of gas yield and carbon conversion, it is found that there are synergistic catalytic effects for K-Ca-Si ternary catalyst, but Si will inhibit the activity of K and Ca. Coupled with SEM and Raman analysis, synergistic mechanism of ternary catalytic system can be revealed. KCl and CaCO3 reduce the graphitization degree of semi-char by reacting with carbon matrix, and CaCO3 can stimulate the pore structure development of semi-char, which accelerate reaction between KCl and carbon matrix to form intermediate active sites, thus favoring gasification reaction and exhibiting a synergistic effect. SiO2, on the other hand, will combine with KCl and CaCO3 to form inert silicates, resulting in the deactivation of KCl and CaCO3. It could be concluded that for high K-high Ca-low Si ternary catalytic system, KCl and CaCO3 would still show a synergistic effect due to higher CaCO3 content than SiO2.

Toward understanding the fractured mechanism in laser welded–brazed Al/steel interface by in–situ SEM tensile observations

In laser welded–brazed Al/steel dissimilar joints, interfacial metallic compound (IMC) had a determined effect on the joint strength. Dynamics interfacial fractured behaviors and generated condition for the IMC which was most beneficial for joint strength (aimed IMC) were hardly defined. This research investigated interfacial fractured behaviors for the joints obtained different laser manufacturing parameters (pure Al, AlSi5, AlSi12 filler metals and different laser powers). In−situ tensile SEM observations was adopted to provide a dynamics observation for the interfacial fractured behaviors. Then fractured behaviors for the joint obtained under coupling parameters of filler metals and laser powers were compared and summarized. It was discovered that aimed IMC was 2–3 µm τ5–Fe1.8Al7.2Si. Then numerical simulation was carried out to calculate the interfacial thermal cycles in order to define its generated thermal condition. Based on this, activity coefficient variations of Fe–Al–Si ternary system due to the addition of alloying element were calculated so as to define its generated metallurgy condition. Experimental results and numerical simulations proved that adding 12 wt% interfacial Si content, maintaining 968°C–1003 °C interfacial peak temperature and keeping 1.64–2.63 s time interaction at high temperature were the metallurgy and thermal conditions for the generation of 2–3 µm τ5–Fe1.8Al7.2Si. This research hoped to provide a reference for determination of interfacial regulation aim in other dissimilar materials joints.

Thermodynamic assessment of La–Fe–Si systems

The phase equilibria of the La–Fe–Si system were investigated using a combination of experimental and thermodynamic modeling methods. The isothermal cross-section of the La–Fe–Si ternary system in the (Fe, Si)-rich region at 1373 K was experimentally investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Based on the experimental results and literature reports of the La–Fe–Si system, the thermodynamic model parameters of the system were optimized using the CALPHAD method. The intermediate compounds in the La–Si binary system and ternary compounds in the La–Fe–Si ternary system were described via sublattice models. The calculated thermodynamic and phase equilibria data were in good agreement with the experimental data, providing a foundation for the development of a multi-component thermodynamic database for LaFeSi-based alloys.

Thermodynamic assessment of the Cr–Mo–Si ternary system

Based on the experimental isothermal sections at 1000 and 1200 °C and the liquidus projection from the measurements by the present authors, the Cr–Mo–Si ternary system is thermodynamically assessed using the CALculation of PHAse Diagram method (CALPHAD). The parameters of the thermodynamic descriptions of all the phases in the Cr–Mo–Si ternary system are optimized on the basis of the reported thermodynamic data and the constitution models of the Cr–Mo, the Cr–Si and the Mo–Si terminal binary systems. Two solution phases, liquid and bcc_A2, were described as substitutional solutions. The intermetallic phases, CrSi, CrSi2 and MoSi2, were modeled by two sublattices, (Cr,Mo):Si, (Cr,Mo):Si2 and (Mo,Cr):Si2, respectively, while βCr5Si3 was modeled by three sublattices (Cr,Mo,Si)2:(Cr,Si)3:Cr3. Cr3Si and Mo3Si have the same crystal structure (cP8, Pm-3n) and present a continuous intermetallic phase M3Si with the two sublattice model (Cr,Mo,Si)3:(Cr,Si)1. Similarly, αCr5Si3 and Mo5Si3 with the same crystal structure (tI32, I4/mcm) form a continuous intermetallic phase M5Si3 with the three sublattice model (Cr,Mo)4:(Cr,Mo,Si)1:(Mo,Si)3. Since the very small solubilities of Cr and Mo, the Diamond-Si phase was treated as a pure element phase. Using the current optimized parameters, the isothermal sections, the liquidus projection and the reaction sequence chart are calculated. The comparison between the calculated results and the experimental investigations, including the isothermal sections, the liquidus projection, and the solidification processes of the as cast alloys, shows that the present calculation can well reproduce the experimental equilibria. The present modeling can finely describe the experimental information of the Cr–Mo–Si ternary system.

Experimental investigation and thermodynamic modeling of the Cr–Zr–Si system

The phase equilibria of the Cr–Zr–Si ternary system were studied combined with the key experiments and thermodynamic assessment. Thirty-five ternary alloys were prepared to determine the isothermal sections at 900 and 1000 °C by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). Five ternary compounds, i.e., τ1 (CrSi2Zr), τ2 (Cr4Si5Zr2), τ3 (Cr4Si7Zr4), τ4 (CrSiZr) and τ5 (Cr3SiZr2), were confirmed. The solubilities of the third element in binary compounds were determined. Based on the experimental phase equilibria data available in the present work and the literature, as well as the thermodynamic parameters of constitutive binary systems, the Cr–Zr–Si system was evaluated by using the CALPHAD (CALculation of PHAse Diagram) method. A set of self-consistent thermodynamic parameters was obtained. Three isothermal sections and liquidus projection were calculated and the reaction scheme was constructed. The calculated results are in agreement with the experimental data.

Dy–Al–Si System: Experimental Study of the Liquid–Solid Phase Equilibria in the Al-Rich Corner

The Dy–Al–Si ternary system has been experimentally studied, as the effect of the dysprosium addition on the constitution and topology of the liquidus surface, focusing on the (Al) rich part. The system has been investigated in a composition range of up to about 58 at% silicon. The alloys constitution and the liquidus surface projection have been determined by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray powder diffraction (XRPD), and differential thermal analysis (DTA). This work is part of a research framework on the properties and solid–liquid phase equilibria of the R Al–Si (R: rare earth) systems. These data, along with the ternary systems isothermal section, are needed to outline the design, plan, and development of new Al–Si-based alloys. In the Dy–Al–Si system, four primary crystallization fields have been experimentally detected: (Si), DyAlxSi(2−x) (orthorhombic form), Dy2Al3Si2 (Τ2), and DyAl(3−x)Six. The following three invariant equilibria have been identified: at 566 °C the ternary eutectic L ⇆ DyAl2Si2 + (Al) + (Si), at 630 °C the U1 L+ DyAl3 ⇆ Dy2Al3Si2 + (Al), and at 562 °C the U2: L+ Dy2Al3Si2 ⇆ DyAl2Si2 +(Al) reactions. A comparison with other known R Al–Si systems has been conducted.

Isothermal section of the Ti–Mn–Si ternary system at 600 °C

Abstract The isothermal section of the Ti–Mn–Si ternary system at 600 °C over the whole composition range has been investigated by means of X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Twenty-five three-phase regions were identified. Four ternary compounds, namely, MnSiTi, MnSi2Ti, Mn5Si4Ti2, and MnSi4Ti, were confirmed in this work. Solid solutions of Mn2Ti with Mn substituted by Si and that of Mn5Si3 with Mn replaced by Ti were observed.

Phases and Interfaces in the Cr–Fe–Si Ternary System: X-ray Diffraction and Electron Microscopy Study

The ternary Cr-Fe-Si system was investigated with X-ray diffraction, energy dispersive X-ray spectrometry, scanning and transmission electron microscopy, and electron diffraction. Samples melted at 1723 K were examined right after cooling or after annealing at 1073 K for 3 days to determine phases, grain sizes, and interphase interfaces. During annealing, a polymorphic transformation of the tetragonal α-FeSi2 to the orthorhombic β-FeSi2 phase occurs, while CrSi2 retains its hexagonal structure at high-temperature treatment. Thin layers of ε-FeSi with a cubic structure were observed and identified within the CrSi2 grains. Crystallographic orientation relationships are determined at the interphase interfaces. The contributions of lattice mismatch and thermal expansion coefficient misfit to deformation are discussed.

Insight into the morphology evolution of dealloyed 3D nanoporous GeSi powder guided by thermodynamic calculations

Dealloying is an effective approach to fabricating nanoporous structures for a variety of applications. The eutectic structure is an excellent precursor for preparing the nanoporous materials with 3D continuous network. Herein, a traditional Al–Ge–Si eutectic system is chosen to investigate the morphology evolution of dealloyed 3D nanoporous GeSi powder by thermodynamic calculations and experiments. Based on the experimental data obtained from the literature and present work, the thermodynamic assessment of the Al–Ge–Si ternary system was carried out by means of the CALPHAD technique. With the guidance of thermodynamic calculations, the composition of the AlGeSi alloy precursors was designed to adjust the 3D GeSi nanoporous materials by dealloying. The morphology evolution of GeSi nanoporous powders was characterized, which revealed that the Ge3Si7 nanoporous powder synthesized from the Al90Ge3Si7 with close-to-eutectic composition as the precursor has the characteristics of smaller pore size and higher specific surface area (382.75 m2/g). The strategy provides a general guide to design other 3D nanoporous structures based on the eutectic systems.

Experimental investigation and thermodynamic calculation in the Al–Be–Si ternary system

Abstract A thermodynamic optimization for the Be– Si system has been performed using the CALPHAD (CALculation of PHAse Diagrams) technique applied to newly measured phase diagram data. The description for this binary system is then combined with the thermodynamic parameters in the Al –Be and Al –Si systems to synthesize a thermodynamic description for the Al –Be –Si ternary system. To verify the reliability of the extrapolated ternary phase diagrams, 11 decisive ternary alloys are prepared by are melting Al, Be and Si pieces and annealing at 530 °C for 8 days. Water-quenched samples are analyzed using differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy with energy dispersive X-ray (SEM/EDX) techniques. The calculated isopleths at 94 wt.% Al, 88 wt.% Al, 50 at.% Al, and 2 wt.% Be are compared with the experimental data from the present work and the literature. The comparisons show that no ternary interaction parameter is needed for the ther-modynamic description of this ternary system. The liquidus projection and reaction scheme are also presented.

Experimental investigation and CALPHAD modeling of the Cu–Cr–Si ternary system

The phase equilibria of the Cu–Cr–Si ternary system were investigated via thermodynamic modeling coupled with key experiments. Seventeen ternary alloys were prepared to determine the isothermal sections of the Cu–Cr–Si system at 700 and 800 °C by combining X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). No ternary compound was found. The solubilities of the third element in binary compounds in the Cu–Si and Cr–Si systems were measured. Based on the thermodynamic descriptions of three constitutive binary systems available in the literature as well as the experimental phase equilibria data obtained from the present work and literature, thermodynamic re-assessment of the Cu–Cr–Si system was carried out by the CALPHAD (CALculation of PHAse Diagrams) approach. The substitutional model and sublattice model were used to describe the solution phases and intermediate phases, respectively. A set of thermodynamic parameters of the Cu–Cr–Si system was obtained. The calculated isothermal sections and vertical section are in good agreement with most of the reliable experimental data. The liquidus projection and reaction scheme of the Cu–Cr–Si system over the whole composition were also presented.

Phase equilibria investigation of the Zr–Cr–Si ternary system

The Zr–Cr–Si ternary system has been investigated over the whole composition by powder X-ray diffraction (PXRD) and scanning electron microscope equipped with energy dispersion spectroscopy (SEM-EDS). The ternary compound Zr4Cr4Si7 has been confirmed to exist in this system and its crystal structure data was acquired by Rietveld method. Rietveld refinement confirms that this ternary phase belongs to the Zr4Fe4Si7-type structure with space group I4/mmm (no.139) and lattice parameter a ​= ​1.3199(6) nm and c ​= ​0.5182(5) nm. The existence of ternary compounds i.e. ZrCrSi2, Zr2Cr4Si5, ZrCrSi and Zr2Cr3Si has also been confirmed at 973 ​K. The solid solubility of Cr in Zr–Si binary compounds and that of Si in α-ZrCr2 and Cr are determined to be between 1.5 ​at. % and 6.8 ​at. %. No remarkable solubility is determined in the other compounds. The results show that there are 19 single-phase regions, 40 two-phase regions and 22 three-phase regions in the studied isothermal section.

Experimental isothermal sections of the ternary phase diagram Al–Cu–Si at 600 °C and 800 °C

The phase diagram of the Al–Cu–Si ternary system was investigated experimentally at the temperatures 600 °C and 800 °C. The current study was designed to contribute to a better understanding of the ternary phase diagram Al–Cu–Si at elevated temperatures, where some of the phase equilibria were only tentatively known. It was found that the ternary phase τ proposed earlier is actually an extended solid solution of Al in the CuSi_δ phase. At 700 °C, the phase CuSi_δ is stable as a pseudo ternary phase, and the existence of a significantly extended thermal stability range in the ternary was also confirmed by DSC measurements. In agreement with previous isothermal sections at other temperatures, a huge solubility of aluminum in CuSi_κ and negligible solubility of Si in AlCu_β was observed.

Experimental investigation of phase equilibria in the Nb–Ni–Si refractory alloy system at 1323 K

Phase equilibria in the Nb–Ni–Si ternary system were experimentally determined at 1323 K and 1473 K using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) techniques. The 1323 K isothermal section of the phase diagram was proposed in combination with previous knowledge of phase stabilities in the system at 1073 K. The results at 1473 K, on the other hand, positively allowed the identification of three new intermetallics phases, not present at lower temperatures, which still need to be crystallographically characterized. The new phases are found in equilibrium either with the Nb5Si3 compound or with the Nb-rich bcc solid solution, which are characterized by very high melting temperatures.

Experimental investigation and thermodynamic modeling of the Cu–Ag–Si ternary system

The phase equilibria of the Cu–Ag–Si system were investigated by a combination of key experiments and thermodynamic modeling. Eighteen ternary alloys were prepared to determine the isothermal sections at 500, 600, and 700 °C of the Cu–Ag–Si system by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The solubilities of Ag in the Cu19Si6, Cu15Si4, Cu56Si11, and hcp(CuSi) phases were measured. No ternary compound was found in this isothermal sections. Based on the experimental equilibria data from the present work, thermodynamic assessment of the Cu–Ag–Si system was carried out by the CALPHAD (CALculation of PHAse Diagrams) approach. The solution phases (Cu), (Ag), (Si), and hcp(CuSi) were described using substitutional solution model and the binary phases Cu19Si6, Cu15Si4, and Cu56Si11 with the solubility of Ag were modeled by the sublattice models. A set of self-consistent thermodynamic parameters of the Cu–Ag–Si system was obtained. The isothermal sections at 500, 600, 650, and 700 °C, vertical sections at 10 and 20 at.% Ag, and liquidus projection were calculated. The reaction scheme of the Cu–Ag–Si system was constructed. The calculated results are in agreement with the experimental data from the present work and literature.

Phase equilibria of (Gd, Er) –Ti–Si systems at high temperatures

ABSTRACTInteractions of rare earth elements with Ti–Si system at high temperatures are of academic interests for the development of refractory lightweight structural materials. As part of the fundamental research of multicomponent Ti–Si-based alloys, solid phase equilibria of the Gd–Ti–Si ternary system at 1073 K and Er–Ti–Si ternary system at 1273 K were investigated through analysis of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Two isothermal sections of the phase diagram and solid solubility of each equilibrium phase have been determined. The ternary compounds i.e. ErTiSi, GdTiSi, Er2Ti3Si4 and Gd1.9Ti3Si4 have been confirmed in the present condition. Binary compound ErSi1-x has not been observed. Ti3Si was confirmed to be nonexistent at both 1073 K and 1273 K. There is no intermetallic compound present in both Gd–Ti and Er–Ti binary systems.

Phase evolution in AlSi20/8009 aluminum alloy during high temperature heating near melting point and cooling processes

Abstract The AlSi20/8009 aluminum alloy was heated to high temperatures near the melting point and cooled to investigate the effect of external Si addition on the phase evolution of Al12(Fe,V)3Si dispersion. Differential scanning calorimeter, scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer were employed. The results showed that Al12(Fe,V)3Si and Si phases evolved into a needle-like Al4.5FeSi phase and a nano-sized V-rich phase during holding the alloy at 580−600 °C. With increasing holding temperature to 620−640 °C, Al4.5FeSi and nano-sized V-rich phases evolved reversibly into Al12(Fe,V)3Si and Si phases, of which Al12(Fe,V)3Si occupied a coarse and hexagonal morphology. During the alloy (after holding at 640 °C) furnace cooling to 570 °C or lower, Si and Al12(Fe,V)3Si phases evolved into strip-like Al4.5FeSi and the V-rich phases, which is a novel formation route for Al4.5FeSi phase different from Al−Fe−Si ternary system.

Phase equilibria of the Cu–Zr–Si system at 750 and 900 °C

Phase equilibria in the ternary Cu–Zr–Si system at 750 and 900 °C have been experimentally investigated via electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) analysis on the equilibrated alloys. The results show the presence of eight three-phase regions at 750 °C and seven three-phase regions at 900 °C. Four ternary phase: τ1 (Zr3Cu4Si6, tI26-Zr3Cu4Si6), τ4 (Zr3Cu4Si4, oI22-Gd3Cu4Ge4), τ5 (ZrCuSi, oP12-Co2Si), and τ6 (Zr3Cu4Si2, 2hP9-Fe2P) were confirmed to exist in the Cu–Zr–Si ternary system at 750 and 900 °C. At 900 °C, the dark gray phase, the chemical composition of which is close to η-Cu3Si, is confirmed to be the liquid phase. Moreover, the solubilities of Cu in ZrSi2, SiZr and Zr3Si2 are considerably small. The solubility of Zr in η-Cu3Si is determined to be negligible. The newly determined phase equilibria of the Cu–Zr–Si system in this work can provide important experimental data for the thermodynamic assessment of the Cu–Zr–Si system and to develop the Cu–Zr–Si alloys and related transition metal silicides.

Theoretical investigations on the U2Mo3Si4 compound from first-principles calculations

With U3Si2 being regarded as a prominent candidate fuel for LWR accident tolerant fuel, the importance on the ternary system such as the U–Mo–Si compounds also arises. However, the properties of the U–Mo–Si ternary system have barely been mentioned by theoretical study up to now. Here a systematic first-principles study for U2Mo3Si4 has been investigated on its structural, electronic, elastic, thermodynamic properties and defect energetics via the density functional theory. The conclusion shows that the U2Mo3Si4 compound is metallic and ductile. The calculated phonon dispersion curve indicates that U2Mo3Si4 is dynamically stable. In addition, the internal energy (E), Helmholtz free energy (F), entropy (S) and heat capacity (CV) are also calculated. The formation energies of different vacancies are obtained. The theoretical investigation in this paper may help with coming up with new thoughts for the design of ternary uranium fuels.