Isothermal Section Diagrams Research Articles

Effects of oxygen partial pressure on the thermodynamics of CaO–SiO2–VOx system at 1873 K

AbstractIn this study, two aspects concerning with the thermodynamics of CaO–SiO2–VOx system were investigated. One aspect is about the effects of oxygen partial pressure on the phase relationships in CaO–SiO2–VOx system at 1873 K, and the other is the measurement of the standard Gibbs energy of formation of the vanadium compounds. In the first aspect, the phase relationships in CaO–SiO2–VOx system at 1873 K under oxygen partial pressure of 1.7 × 10−9 atm were determined, and the isothermal section diagram was constructed. Furthermore, by comparing this diagram with that under 6.9 × 10−11 atm, the effects caused by oxygen partial pressure on this system were elucidated. With the increase in oxygen partial pressure, the compound CaV2O4 that exists stably under 6.9 × 10−11 atm is oxidized to V2O3 and CaVO3. The solubility limit of V2O3 in liquid phase also increases remarkably, which results in the enlargement of the single liquid area. In the second aspect, the standard Gibbs energy of formation of CaV2O4, CaVO3, V2O3, and Ca2Si1−δVδO4 (0 < δ < 0.1) at 1873 K were measured. The determined values for CaV2O4 and CaVO3 are −1 259 468.9 ± 5090.5 J/mol and −963 479.8 ± 3298.6 J/mol, respectively. Then, the limit of oxygen partial pressure for CaV2O4 existing stably at 1873 K is determined to be 4.4 × 10−10 atm.

Exploitation of Mold Flux for the Ti-bearing Welding Wire Steel ER80-G

AbstractIn order to improve the surface defects of strand, the mold flux is exploited for the Ti-bearing welding wire steel ER80-G. The composition of mold flux is designed by analyzing the solidification characteristics of ER80-G and the slag system isothermal section diagram, simulating by the FactSage thermodynamics software. The Ti-bearing welding wire steel ER80-G belongs to the peritectic steel. The melting point range of the newly designed mold flux system is from 1030∘C to 1129∘C, the melting rate range is from 58 s to 64 s, the viscosity range at the temperature of 1300∘C is from 0.33 Pa·s to 0.50 Pa·s, the crystallization temperature range is from 1160∘C to 1293∘C, the crystalline fraction range is from 34% to 85%. The surface defects of strand which transverse depression, longitudinal depression, slag runner and so on were obviously improved when the newly design mold flux F3, F5, F9 were used to the production respectively. Those results suggest that 0.9 basicity with 28.4%-CaO, 31.6%-SiO2,3%-MgO, 10%-Na2O, 10%-CaF2, 6%-Al2O3, 1%-Fe2O3, 10%-Tcand all groups with 1.0 and 1.1 basicity show the best properties for Ti-bearing welding wire steel ER80-G.

Thermodynamics of the CaO–SiO2–VOx system at 1873 K under the oxygen partial pressure of 6.9×10−11 atm

AbstractBased on the phase equilibria of the CaO–SiO2–VOx system determined experimentally at 1873 K and the oxygen partial pressure of 6.9×10−11 atm, the isothermal section diagram of the system was constructed. Aside from the simple oxides SiO2 and V2O3, three complex crystal phases CaV2O4, Ca2SiO4 dissolving V2O3, and CaVO3 dissolving SiO2 were found in the present investigated composition range. The solubility of V2O3 in Ca2SiO4 phase can reach 5 mass %, and the CaVO3 phase dissolves about 5% mass SiO2. Furthermore, the thermodynamic activities of VOx and SiO2 in the determined single liquid region were measured by equilibrating the melts with liquid copper. The activity coefficient of SiO2 decreases linearly with the increase in the basicity of the melts and is almost irrelevant to the total content of vanadium oxides. The activities of vanadium oxides increase slightly with the increase in the basicity but are mainly determined by the total content of vanadium oxides in the melts. With the increase in the basicity, the activity coefficient of VO1.5 increases almost linearly, whereas those of VO2 and VO2.5 decrease gradually.

Formation Mechanism of CaS-Bearing Inclusions and the Rolling Deformation in Al-Killed, Low-Alloy Steel with Ca Treatment

Abstract The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.

New compounds and phase equilibria in the Zr–Ti–P system

The interaction between components in the Zr–Ti–P system in the range of up to 67at.% P was analyzed and the isothermal section diagram at 1070K was constructed from X-ray structural and EDS analysis. Solid substitutional solutions based on the binary phosphides M3P with the Ti3P-type structure (Ti3.0−2.3Zr0−0.7P and Zr3.0−2.5Ti0−0.5P) were found. The phosphide (Ti,Zr)2P with the Co2Si-type structure is homogeneous at the Zr1.2−0.6Ti0.8−1.4P composition. From powder X-ray diffraction methods, the crystal structure of ZrTiP0.68 was shown to be of the Zn3Cu-type (space group P-6, a=0.47600(1), c=0.30038(1)nm, RI=0.0444); HfTiP0.68 is isostructural. These compounds are homogenous in the range Zr1.0−1.5Ti1.0−0.5P0.68 and Hf0.9−1.2Ti1.1−0.8P0.68. From single-crystal methods, the structure of Zr0.93Ti0.07P0.93 was determined to belong to the WC-type structure (space group P-6m2, a=0.3004(2), c=0.3117(3) nm, RF=0.0228).

Phase Equilibria and Ternary Intermetallic Compound with L12 Structure in Co-W-Ga System

Phase equilibria and stabilities of intermetallic phases appearing in the Co-rich portion of the Co-W-Ga ternary alloys were investigated and isothermal section diagrams at 1200, 1100, 1000, and 900 °C were determined. A fine cuboidal phase with an L12 structure was observed at 900 and 800 °C, where the composition of the new ternary compound obtained by aging at 900 °C for the Co-7.4W-12.0Ga alloy was Co-11.2W-11.4Ga (at.%). It was confirmed that this compound is metastable at 900 °C but is more stable at 800 °C. These results mean that the thermodynamic stability of the metastable Co3W L12 phase, especially in the low temperature region, increases by the addition of Ga.

Separation of Fe and Sn–Cu Phases in an Fe–Sn–Cu–B System

Scrap metal often includes a large amount of copper and tin. It is important to recover copper and tin from this scrap metal for recycling. Separation into two liquid phases, namely Fe and Sn(-Cu) phases, has been investigated at 1523 K in Fe-Sn-B and Fe-Sn-Cu-B systems. In the Fe-Sn-B system, the tin content of the Fe-rich phase and the iron content of the Sn-rich phase are 13.7 and 11.7 mass%, respectively, when [mass%B] (in Fe) = 3.62. Boron widens the miscibility gap of the Fe-Sn binary system. The isothermal section diagram of the Fe-Sn-Cu-2.66 mass%B quaternary system at 1523 K is described. In the Fe-Sn-Cu-B system, separation into two liquid phases, Fe-rich and [Sn-Cu]-rich, is found over all ratios of [mass%Sn]/[mass%Cu]. The separation region is enlarged as the [mass%Sn]/[mass%Cu] ratio is decreased. By using the separation into two liquid phases, iron can be enriched in the Fe-rich phase and copper and tin can be enriched in the [Sn-Cu]-rich phase. It is possible to recover copper and tin effectively from Fe-Sn-Cu alloy.

Experimental investigation and thermodynamic calculation of phase equilibria in the Sn-Au-Ni system

The phase equilibria of the Sn-Au-Ni system, including six isothermal section diagrams in the Sn-rich portion at 200–600°C, as well as three vertical sections at Au:Ni=1:1, 50at.%Sn, and 40at.%Sn, were investigated by means of differential scanning calorimetry (DSC), x-ray diffraction, and metallography. The experimental results indicated that (1) there exists a ternary compound Sn4AuNi2 that is stable up to about 400°C, (2) there are larger solubilities of Au in the Ni3Sn2 phase in the Sn-Ni system and Ni in the SnAu phase in the Sn-Au system, and (3) there is the two-phase equilibrium between Sn2Ni3 and SnAu compounds below 400°C, rather than the continuous phase region from the Sn2Ni3 to the SnAu phases reported previously. Thermodynamic assessment of the Sn-Au-Ni system was also carried out by using the calculation of phase diagrams (CALPHAD) method, in which the Gibbs energies of the liquid, fcc, and hcp phases are described by the subregular solution model and that of compounds, including a ternary compound, are represented by the sublattice model. The thermodynamic parameters for describing each phase were optimized and good agreement between the calculated and experimental results was obtained.

Thermodynamic Study of Phase Equilibria in the Ni–Fe–B System

The phase equilibria in the Ni-Fe-B ternary system have been studied experimentally and using thermodynamic calculations. The Gibbs energy of the individual phases was described by the regular solution approximation and the two-sublattice model. The thermodynamic parameters for each phase were evaluated using the experimental data on phase boundaries obtained from differential scanning calorimetry (DSC) and other available literature data. The evaluated parameters enabled us to obtain reproducible calculations of the isothermal section diagrams. The calculated isopleth at the 26 mol% B section agreed with the DSC data obtained in this study, whereas the calculated liquidus and sulidus temperatures were higher than the reported values at the Ni 2 B-Fe 2 B pseudo-binary section.

Phase equilibria and the related properties of Sn-Ag-Cu based Pb-free solder alloys

We have recently developed a thermodynamic database for micro-soldering alloys which consists of the elements Pb, Bi, Sn, Sb, Cu, Ag, Zn, and In. In this paper, the phase equilibria and the related thermodynamic properties of the Sn-Ag-Cu base alloys are presented using this database, alloy systems being one of the promising candidates for Pb-free solders. The isothermal section diagrams of the Sn-Ag-Cu ternary system were experimentally determined by SEM-EDS, x-ray diffraction and metallographic techniques. Based on the present results as well as the previous data on phase boundaries and thermochemical properties, thermodynamic assessment of this system was carried out. The isothermal and vertical section diagrams, liquidus surface, mass fractions of the phase constitution, etc., were calculated. The predictions of surface energy and viscosity were also investigated. Moreover, a non-equilibrium solidification process using the Scheil model was simulated and compared with the equilibrium solidification behavior in some Sn-Ag-Cu base alloys. Calculated results based on the Scheil model were incorporated into a three-dimensional solidification simulation and the prediction of practical solidification procedures was performed.

Phase equilibria and Heusler phase stability in the Cu-rich portion of the Cu–Al–Mn system

Results pertaining to the phase equilibria between the phases α (A1), β (A2, B2 or L2 1(D0 3)) and γ (γ-bronze type), and the two-stage order–disorder transition and decomposition reaction A2–B2–L2 1 in the ternary system Cu–Al–Mn are reported. Ternary isothermal section diagrams at 800, 700, 600 and 550°C have been constructed using Energy Dispersion X-ray Spectrometry (EDX) analysis results, and it is found that the β single-phase region in the Cu–Al system is very significantly widened on increasing the Mn content. The critical temperatures ( T c) of the A2–B2–L2 1 order–disorder transitions, determined by Differential Scanning Carolimetory (DSC) analysis are found to be strongly dependent on the Al content rather than on the Mn content. It is confirmed by DSC measurements and TEM-EDX analysis that a miscibility gap island between Cu 3Al and Cu 2AlMn phases exists in the L2 1 phase region. The second order ordering reaction between D0 3 and L2 1 structures has also been detected by X-ray diffraction. The stability of the bcc β phase is discussed in terms of atomic and magnetic ordering.

Phase equilibria and microstructural control in the Ni-Co-Al system

This paper is a report of the results of investigations on the phase equilibria among γ(Al), and γ′ (Ll2) and β(B2) phases, β → β′ (Ll0) martensitic transformation temperatures, and microstructural features of multi-phase alloys fabricated through various thermo-mechanical processes in the Ni−Co−Al system. The isothermal section diagrams and tie line configurations of 900, 1100 and 1300°C was determined by energy dispersion X-ray spectrometry (EDX) analysis. The Ms temperature was measured by differential scanning calorimetry (DSC) analysis and a contour of iso-Ms composition lines was determined. On the basis of this information, the various types of microstructure of β + γ, β + γ′ and β + γ + γ′ phases was obtained through thermo-mechanical treatment. Morphological features of the multi-phase alloys with fine blocky, plate, Widmanstatten and lamellar structures was discussed in connection with heat-treatment, phase diagram and martensitic transformation. Mechanical properties were also examined and a good combination of strength and ductility was obtained in the multi-phase alloys.

BaO-Fe<SUB>2</SUB>O<SUB>3</SUB>-(0∼50 mol%)B<SUB>2</SUB>O<SUB>3</SUB>擬三元系の液相面と973 Kの等温状態図

BaO-Fe<SUB>2</SUB>O<SUB>3</SUB>-(0∼50 mol%)B<SUB>2</SUB>O<SUB>3</SUB>擬三元系の液相面と973 Kの等温状態図

Construction of the Isothermal Section Diagram of Ternary System with an Improved Method of Compound Synthesis

Construction of the Isothermal Section Diagram of Ternary System with an Improved Method of Compound Synthesis

Experimental and theoretical phase diagrams of the iron-rich Fe-Si-Ge ordering system

The phase separation in iron-rich Fe-Si-Ge ternary alloys was investigated by means of transmission electron microscopy. The phase separations into A2 and D03 were recognized in several alloys in addition to the phase separation into B2 and D03 which has already been found in Fe-Si and Fe-Ge binary systems. On the basis of TEM observations, isothermal section diagrams are proposed for the iron-rich corner at 823, 873, 923 and 973 K. The A2 + D03 two-phase field exists in a band-shaped region at 823 K. With increase in temperature,the A2 + D03 field gradually shrinks and is eventually replaced at 973 Kwith the B2 + D03 field, which extends from both the Fe-Si and Fe-Ge binary sides. The phase diagrams were well reproduced by the calculations based on the so-called Bragg-Williams-Gorsky approximation, taking account of the chemical and magnetic pair interactions up to the second nearest neighbour. The effects of the magnetism on the equilibria are discussed.