The liquidus surface and tie-lines in the iron-nickel-sulfur system between 1473 and 1673 K

The liquidus compositions and the tie-lines for the solid alloy plus liquid sulfide two-phase region were determined for the iron-nickel-sulfur system in the temperature range 1473 to 1673 K. Experiments were conducted by sampling the liquid sulfide in equilibrium with the alloy phase and chemically analyzing the sulfide. The alloy was quenched and analyzed by electron microprobe. The results represent a significant revision to existing data.     

The liquidus surface and tie-lines in the iron-nickel-sulfur system between 1473 and 1673 K

The liquidus compositions and the tie-lines for the solid alloy plus liquid sulfide two-phase region were determined for the iron-nickel-sulfur system in the temperature range 1473 to 1673 K. Experiments were conducted by sampling the liquid sulfide in equilibrium with the alloy phase and chemically analyzing the sulfide. The alloy was quenched and analyzed by electron microprobe. The results represent a significant revision to existing data.     

The metal saturation line and tie-lines in the nickel-cobalt-sulfur ternary system between 1273 and 1573 K

The metal saturation line and the tie-lines in the Ni-Co-S ternary system have been determined between 1273 and 1573 K. The experiments were conducted by equilibrating the liquid sulfide with the metallic alloy phase. The liquid sulfide phase was sampled and chemically analyzed. The alloy was analyzed by electron microprobe. Combining the present results with the available literature data, the thermodynamic properties of this system were calculated.     

The liquidus surface of the system titanium-copper-silver

Conclusions The liquidus surface of the system titanium-copper-silver was studied by metallographic and thermal analysis methods. Projections were constructed of liquidus surface isotherms on the plane of the concentration triangle, and the shape of the simultaneous-crystallization curves of various phases (boundary curves) was determined.Translated from Poroshkovaya Metallurgiya, No. 4 (88), pp. 44–48, April, 1970.     

A thermodynamic analysis of the copper-lead-sulfur system at 1473 K

A consistent set of thermodynamic activities in the Cu-Pb-S system is derived at 1473 K from a knowledge of the high-temperature phase relations, the boundary binary thermodynamics and the estimated limiting activity coefficients of sulfur in copper-lead melts. Within the uncertainty limits, the derived values in the present study and the experimental values of Azuma,et al, for the activity of Pb are in good accord. The tie-line distribution in the lead-rich portion of the ternary miscibility gap has been slightly modified to be consistent with the thermodynamic properties of the lead-sulfur system.     

A thermodynamic analysis of the copper-lead-sulfur system at 1473 K

A consistent set of thermodynamic activities in the Cu-Pb-S system is derived at 1473 K from a knowledge of the high-temperature phase relations, the boundary binary thermodynamics and the estimated limiting activity coefficients of sulfur in copper-lead melts. Within the uncertainty limits, the derived values in the present study and the experimental values of Azuma,et al, for the activity of Pb are in good accord. The tie-line distribution in the lead-rich portion of the ternary miscibility gap has been slightly modified to be consistent with the thermodynamic properties of the lead-sulfur system.     

Examination of solidification pathways and the liquidus surface in the Nb-Ti-Al system

The solidification pathways, subsequent solid-state transformations, and the liquidus surface in the Nb-Ti-Al system have been examined as part of a larger investigation of phase equilibria in Nb-Ti-Al intermetallic alloys. Fifteen alloys ranging in composition from 15 to 40 at. pct Al, with Nb to Ti ratios of 4:1, 2:1, 1.5:1, 1:1, and 1:1.5, were prepared by arc melting and the as-cast microstructures were characterized by optical microscopy (OM), microhardness, X-ray diffraction (XRD), differential thermal analysis (DTA), backscattered electron imaging (BSEI), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). The results indicate that the range of primary β solidification is much wider than that indicated in previously reported liquidus surfaces, both experimental and calculated. Differential thermal analysis has identified the existence of a β to σ+γ transformation in three alloys where it was previously thought not to exist; confirmation was provided by high-temperature vacuum heat treatments in the single-phase β region followed by rapid quenching. The location of the boundary between the β, σ, and δ primary solidification fields has been redefined. A massive β → δ transformation, which was observed in the cast microstructure of a Nb-25Ti-25Al alloy, was repeatable through cooling following homogenization. A β → δ+σ eutectoid-like transformation in the 25 at. pct Al alloys, was detected by DTA and evaluated through microstructural analysis of heat-treated samples. Trends in the β phase with variations in composition were established for both lattice parameters and microhardness. As a result of this wider extent of the primary β solidification field, a greater possibility exists for microstructural control through thermal processing for alloys consisting of either σ+γ, β+σ, or β+δ phases. An erratum to this article is available at .     

Thermodynamic observations of the molten FeS-FeO system and its vicinity at 1473 K

The Fe-S-O melts were equilibrated with the CO-CO₂-SO₂ gases at 1473 K under a S₂ (g) partial pressure of 0.0004 atm (=0.041 kPa). This S₂ isobar runs on both sides of the pseudobinary FeS-FeO system, thus adding a continuous extension to the isobaric network of S₂ and O₂ in the literature. The activities of S₂ (g), O₂ (g), Fe (γ), FeS (L), FeO (L), FeO_1.33 (s), and FeO_1.5 (s) were calculated in the vicinity of the pseudobinary FeS-FeO melt. The activity of magnetite FeO_1.33 (s) was observed to be greater than that of FeO (L) in the ferrous binary FeS-FeO melts containing 35 to 55 mol pct FeO.     

Compressive strength and creep properties of Ir-Nb-Zr alloys between 1473 and 2073 K

The microstructure and strength at 1473 and 2073 K and creep properties at 2073 K were investigated in three Ir-Nb-Zr alloys with the fcc and L1₂ two-phase structure. The microstructure and lattice misfit were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometry (XRD). Compression and creep tests were performed, and their deformation structures were observed using SEM and TEM. At 1473 K, the strength of the Ir-Nb-Zr alloys was higher than that of the binary Ir-Nb and Ir-Zr alloys, but they were almost equivalent at 2073 K. However, the ternary alloys showed great improvement on creep at 2073 K. The time for the 2 pct creep strain of the Ir-Nb-Zr alloy was about 100 hours, while it was 1 hour for the binary alloys. The deformation mechanisms for compressive strength and creep resistance in these Ir-Nb-Zr alloys are discussed in terms of the deformation structure. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

The Fe-rich corner of the metastable C-Cr-Fe liquidus surface

The liquidus surface of the C-Cr-Fe system has been experimentally determined in the Fe-rich region —C ≤6 wt pct, Cr ≤40 wt pct —using a sensitive differential thermal analysis technique, along with optical and scanning electron microscopy and X-ray diffraction. Previous liquidus surfaces for this system have differed on the extent of the (Cr,Fe)₂₃C₆ liquidus field, with one version reporting its existence at ∼20 wt pet Cr, and others finding that it did not occur at Cr levels of less than ∼60 wt pct. The present investigation provides evidence in favor of the second contention, with the (Cr,Fe)₂₃C₆ field not being detected at Cr ≤40 wt pct. Changes are proposed to the accepted liquidus surface in respect of the compositions of the invariant reactions—L + αδFe ⇌γFe + (Cr,Fe)₇C₃ andL + (Cr,Fe)₇C₃ ⇌γFe + (Fe,Cr)₃C —and of the monovariant eutectic valley—L⇌ γFe + (Cr,Fe)₇C₃.     

Spinel-corundum equilibria and activities in the system MgO-Al2O3-Cr2O3 at 1473 K

The tie-lines delineating intercrystalline ion-exchange equilibria between MgAl₂O₄-MgCr₂O₄ spinel solid solution and Al₂O₃-Cr₂O₃ solid solution with corundum structure have been determined at 1473 K by electron microprobe and X-ray diffraction (XRD) analysis of equilibrated phases. The tie-lines are skewed to the solid solution 0.7MgAl₂O₄-0.3MgCr₂O₄. The lattice parameters and molar volumes of both the solid solution series exhibit positive deviations from Vegard’s and Retger’s laws, respectively. Activities in the spinel solid solution are derived from the tie-line information and thermodynamic data on Al₂O₃-Cr₂O₃ solid solution available in the literature. Activities of Mg_0.5CrO₂ and Mg_0.5AlO₂ in the spinel solid solution exhibit strong positive deviations from Raoult’s law over most of the composition range. However, activity of Mg_0.5CrO₂ exhibits mild negative deviation for compositions rich in Mg_0.5CrO₂. The activity-composition relationship in the spinel solid solution is analyzed in terms of the intracrystalline exchange of cations between the tetrahedral and octahedral sites of the spinel structure. The intracrystalline ion exchange is governed by site preference energies of the cations. The difference between the Gibbs energy of mixing calculated using the cation mixing model and the experimental data is taken as a measure of the strain contribution arising from the difference in the radii of Al³⁺ and Cr³⁺ ions. The large positive strain enthalpy suggests the onset of immiscibility in the spinel solid solution at low temperatures. The computed critical temperature and composition for phase separation are 802 (±20) K and =0.46 (±0.02), respectively.     

Investigation of the surface of the liquidus of the Fe-Ni-S system at X s<0.51

Methods of thermal analysis, X-ray, optical, and electron microscopy were used to study the liquidus surface of the Fe-Ni-S system in the field of 35 to 51 at. pct sulfur. The FeS-NiS, FeS-Ni₃S₂, Fe_0.55S_0.45-Ni_0.55S_0.45, and Fe_0.61S_0.39-Ni_0.61S_0.39 sections and some additional samples were examined. A microscopic study of the samples slowly cooled and annealed enabled referring of all the samples to the fields of primary crystallization of the monosulfide solid solution (Fe _x Ni_1−x )S_1+y (MSS), the Fe-Ni solid solution with the γ-Fe structure (TN), and the (Fe _x Ni_1−x )_3±y S₂ heazlewoodite solid solution (HZSS). The data, obtained by a method of derivative thermal analysis, have been used to describe analytically the MSS and HZSS surface of primary crystallization. Previous results were used together with our own data to construct the TN surface of primary crystallization. These parts of the liquidus surface have been approximated by polynomial equations, the coefficients of which were determined by the least-squares method. As a result of the absence of experimental data in the δ-Fe-based solid-solution primary crystallization field, this liquidus part is approximated on the basis of the Fe-S and Ni-Fe phase diagram data. The equations are used to construct the boundaries between various areas of phase primary crystallization, to define the coordinates of a triple point, and to construct isotherms.     

Calculation of the liquidus of the Mo-C system

Conclusions Existing data on the Mo-C system make it possible to construct a consistent system of models of thermodynamic properties of phases. To obtain satisfactory agreement between calculated phase equilibrium lines and experimental results, it is necessary to allow for the solubility of carbon in molybdenum. The system of phase models enables the parameters of low-temperature solid-state transformations (in particular MoC formation) to be estimated.Translated from Poroshkovaya Metallurgiya, No. 4(268), pp. 37–42, April, 1985.     

Phase Equilibrium of the System CaO‐P2O5‐SiO2 between 1473 K and 1673 K

Phase equilibrium was investigated in the ternary system of CaO‐P₂O₅‐SiO₂ at 1473K, 1573K and 1673K.     

Interaction Parameter e for Carbon‐saturated Liquid Iron between 1623 and 1723 K

In order to derive the values of the interaction parameter, , in carbon‐saturated {Fe‐C} liquid alloys, as defined below; an electrochemical technique incorporating zirconia solid electrolyte was applied for the direct measurements of the Henrian activities of oxygen, h_O, between 1623 and 1723 K, while the concentrations of oxygen and carbon in pct by weight, [%O] and [%C]_Sat, respectively, were determined by using a conventional LECO analyzer. The results can be summarized as      

Approximation of the liquidus surface of the HfO2-Y2O3-CaO system by reduced polynomials

Translated from Poroshkovaya Metallurgiya, No. 12, pp. 50–55, December, 1990.