Phase equilibria in the ternary Al-Sc-Mn system

Optical microscopy, electron microprobe analysis, and electrical resistivity measurements are used to study Al-Sc-Mn alloys containing up to 3 at % Sc and to 2.5 at % Mn. The boundaries of the Al-based solid solution are determined at 640, 600, and 400°C, and the isothermal section of the Al-rich portion of the Al-Sc-Mn system at 640°C is constructed. The Al-based solid solution is found to be in equilibrium with the ScAl₃ and MnAl₆ phases.     

Phase equilibria in the ternary system zirconium-molybdenum-carbon

Summary The system Zr-Mo-C was investigated by means of x-ray diffraction and microstructural analyses. Phase equilibria in the system at 1400 and 600°C were established (Fig. 1). The compound Mo₂C dissolves about 4 at.% Zr. The ZrC-base solid solution extends up to 90 mol.% Mo₃C₂. The hexagonal phase Mo₃C₂ may be stabilized at 1400°C and below by zirconium.     

Phase relations in the system Cu-Gd-O

The phase relations in the system Cu-Gd-O have been determined at 1273 K by X-ray diffrac- tion, optical microscopy, and electron microprobe analysis of samples equilibrated in quartz ampules and in pure oxygen. Only one ternary compound, CuGd₂O₄, was found to be stable. The Gibbs free energy of formation of this compound has been measured using the solid-state cell Pt, Cu₂O + CuGd₂O₄ + Gd₂O₃ // (Y₂O₃) ZrO₂ // CuO + Cu₂O, Pt in the temperature range of 900 to 1350 K. For the formation of CuGd₂O₄ from its binary component oxides, CuO (s) + Gd₂O₃ (s) → CuGd₂O₄ (s) ΔG° = 8230 - 11.2T (±50) J mol^-1 Since the formation is endothermic, CuGd₂O₄ becomes thermodynamically unstable with respect to CuO and Gd₂O₃ below 735 K. When the oxygen partial pressure over CuGd₂O₄ is lowered, it decomposes according to the reaction 4CuGd₂O₄ (s) → 4Gd₂O₃ (s) + 2Cu₂O (s) + O₂ (g) for which the equilibrium oxygen potential is given by Δμ_{o 2} = −227,970 + 143.2T (±500) J mol⁻¹ An oxygen potential diagram for the system Cu-Gd-O at 1273 K is presented.     

Phase relations in the system Pb-Sn-Se

Phase equilibria have been determined in the portion of the Pb-Sn-Se system bounded by the compositions Pb-Sn-SnSe-PbSe. The PbSe-SnSe join is quasibinary with only small deviations from stoichiometry. The ternary phase boundaries lie close to the Pb-Sn side of the diagram. Subsolidus relations are shown by a series of isoplethal sections.     

Phase diagram of the ternary NaF-LiF-LaF3 system

Differential thermal and X-ray diffraction analyses are used to study the phase equilibria in the ternary NaF-LiF-LaF₃ system. A ternary eutectic and two peritectics are found. The solid eutectic mixture whose melting temperature is 580°C consists of NaLaF₄ chemical compound crystallites and individual lithium and sodium fluorides (LiF, NaF). Above the melting point, LaF ₆ ^3? complex anions form in the melt at 590–750°C.     

Al-Ni-Er三元体系相平衡研究

高强铝合金具有密度低、强度高、热加工性能好等优点,是航空航天领域的主要结构材料.现代航空航天工业的发展,对高强铝合金的强度和综合性能提出了更高要求.研究和应用双相纳米结构铝合金离不开精确可靠的相图信息.通过X射线衍射(XRD),扫描电子显微镜(SEM)和电子探针显微分析(EPMA/WDS),对Al-Ni-Er三元体系在...     

Phase equilibria and intermetallic phases in the Ni-Si-Mg ternary system

The Ni-Si-Mg ternary phase diagram has been established after homogenization and slow cooling to room temperature. The chemical compositions of the alloys and their phases were obtained using fully quantitative energy dispersive X-ray spectroscopy (EDS) with standard spectrum files created from intermetallic compounds Mg₂Ni and Ni₂Si. The following intermetallic phases have been observed: (a) four new ternary intermetallic phases, designated as ν, ω, μ, and τ, (b) a ternary intermediate phase Mg(Ni,Si)₂ based on the binary MgNi₂ phase containing Si; (c) three ternary intermetallic phases, η, κ, and ζ, previously reported by the present authors;[10] and (d) Mg₂SiNi₃ (Fe₂Tb type),^[9] previously reported by Noreus et al. ^[8] The MgNi₆Si₆ phase, which was also previously reported,^[7] was not observed at the corresponding composition in the present work. However, the MgNi₆Si₆ phase reported as being of hexagonal symmetry (Cu₇Tb type),^[9] with the lattice parameters a=0.4948 nm and c=0.3738 nm, possibly corresponds to the μ phase (Mg(Si_0.48Ni_0.52)₇) discovered in the present work. The lattice structure of the newly discovered ω phase was determined with the help of the X-ray indexing program TREOR (developed by Werner et al. ^[13]) to be a hexagonal structure of the Ag₇Te₄ type ((Mg_0.52Ni_0.48)₇Si₄) with the lattice parameters a=1.3511 nm and c=0.8267 nm.     

Phase relations and gibbs energies in the system Mn-Rh-O

Phase relations in the system Mn-Rh-O are established at 1273 K by equilibrating different compositions either in evacuated quartz ampules or in pure oxygen at a pressure of 1.01 × 10⁵ Pa. The quenched samples are examined by optical microscopy, X-ray diffraction, and energy-dispersive X-ray analysis (EDAX). The alloys and intermetallics in the binary Mn-Rh system are found to be in equilibrium with MnO. There is only one ternary compound, MnRh₂O₄, with normal spinel structure in the system. The compound Mn₃O₄ has a tetragonal structure at 1273 K. A solid solution is formed between MnRh₂O₄ and Mn₃O₄. The solid solution has the cubic structure over a large range of composition and coexists with metallic rhodium. The partial pressure of oxygen corresponding to this two-phase equilibrium is measured as a function of the composition of the spinel solid solution and temperature. A new solid-state cell, with three separate electrode compartments, is designed to measure accurately the chemical potential of oxygen in the two-phase mixture, Rh + Mn_3−2xRh_2xO₄, which has 1 degree of freedom at constant temperature. From the electromotive force (emf), thermodynamic mixing properties of the Mn₃O₄-MnRh₂O₄ solid solution and Gibbs energy of formation of MnRh₂O₄ are deduced. The activities exhibit negative deviations from Raoult’s law for most of the composition range, except near Mn₃O₄, where a two-phase region exists. In the cubic phase, the entropy of mixing of the two Rh³⁺ and Mn³⁺ ions on the octahedral site of the spinel is ideal, and the enthalpy of mixing is positive and symmetric with respect to composition. For the formation of the spinel (sp) from component oxides with rock salt (rs) and orthorhombic (orth) structures according to the reaction, MnO (rs) + Rh₂O₃ (orth) → MnRh₂O₄ (sp),ΔG° = -49,680 + 1.56T (±500)J mol⁻¹ The oxygen potentials corresponding to MnO + Mn₃O₄ and Rh + Rh₂O₃ equilibria are also obtained from potentiometric measurements on galvanic cells incorporating yttria-stabilized zirconia as the solid electrolyte. From these results, an oxygen potential diagram for the ternary system is developed.     

Phase equilibria in Nb-Y-Si ternary system at 873 K

The isothermal section of the Nb-Y-Si ternary system at 873 K was investigated over the whole concentration range mainly by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). This isothermal section consisted of 10 single-phase regions, 17 two-phase regions, and 8 three-phase regions. The existence of the binary compounds, i.e., Y 5 Si 3 , Y 5 Si 4 , YSi, Y 3 Si 5 , YSi 2 , Nb 5 Si 3 and NbSi 2 at 873 K was confirmed. On the basis of XRD patterns, the structure types of Y 5 Si 4 , Y 3 Si 5 and YSi 2 were discussed. No ternary compound and no detectable solid solubility in the binary compounds were found.     

Phase relations and crystallographic data for the Pr-Zn system

Metallographic, thermal, X-ray, and resistivity data were employed in establishing the phase diagram of the Pr-Zn system. Eight compounds, three eutectics, and a eutectoid were observed. The compounds PrZn, PrZn₂, and Pr₂Zn₁₇ melt congruently at 882°, 898°, and 978°C, respectively. The compounds PrZn₃, Pr₃Zn₁₁, PrZn_4.46, Pr₃Zn₂₂, and PrZn₁₁ undergo peritectic decomposition at 833°, 855°, 891°, 956°, and 743°C, respectively. The eutectic temperatures and compositions in wt pct Zn are 576°C and 11.9 pct, 833°C and 39.0 pct, and 830°C and 56.8 pct. The eutectoid reaction occurs at 558°C and 5.2 pct Zn. The lattice parameters of the compounds in the system were determined using X-ray powder diffraction methods. Single crystal X-ray techniques were used to show that PrZn₃ has the YZn₃ (space group Pnma) type structure.     

Phase equilibria in the Mg-Al-Ca ternary system at 773 and 673 K

The isothermal sections of the Mg-Al-Ca ternary system at 773 and 673 K were determined by phase analysis with electron-probe microanalysis (EPMA) and transmission electron microscopy (TEM). The C36 phase exists between the C14 (Mg₂Ca) and C15 (Al₂Ca) phases, and its stoichiometry is close to Mg₂Al₄Ca₃. The α-Mg phase equilibrates with the C14 and C36 phases at 773 K, but with C14, C15, and β phases at 673 K, due to the decomposition of the C36 phase into C14 and C15 phases. These intermetallic phases have significant solid-solubility in the ternary system.     

Phase relations in the system CaO-SiO2-ZrO2 at 1573 K

Zirconia-based solid electrolytes with zircon (ZrSiC₄) as the auxiliary electrode have been suggested of sensing silicon concentrations in iron and steel melts. A knowledge of phase relations in the ternary system MO-SiO₂-ZrO₂ (M = Ca, Mg) is useful for selecting an appropriate auxiliary electrode. In this investigation, an isothermal section for the phase diagram of the system CaO-SiO₂ZrO₂ at 1573 K has been established by equilibrating mixtures of component oxides in air, followed by quenching and phase identification by optical miroscopy, energy disperse analysis of X-rays (EDAX) and X-ray diffraction analysis (XRD). The equilibrium phase relations have also been confirmed by computation using the available thermodynamic data on condensed phases in the system. The results indicate that zircon is not in thermodynamic equilibrium with calcia-stabilized zirconia or calcium zirconate. The silica containing phase in equilibrium with stabilized zirconia is Ca₃ZrSi₂O₉. Calcium zirconate can coexist with Ca₃ZrSi₂Og and Ca₂SiO₄.     

Phase equilibria in the ternary system Sc−Cr−C at subsolidus temperatures

Phase equilibria in the ternary system Sc−Cr−C were investigated by metallography, differential thermal analysis, x-ray diffraction, and electron probe microanalysis. A projection of the solidus surface was constructed for the first time. The nature of phase equilibria in the system is defined by the presence of two thermodynamically stable phases based on the compounds Sc₂CrC₃ (whose existence was confirmed) and ScC_1−x. The melting point of the alloys increases with increasing carbon concentration. Compositions in the 〈Cr〉+〈ScC_1−x〉+〈Sc〉 range have a minimum melting temperature equal to 1018±2°C, and the maximum melting temperature in the system, 1660±2°C, is found in alloys containing 〈Cr₃C₂〉+〈Sc₂CrC₃〉+C. Institute for Materials Science Problems. Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 18–26, March–April, 1997.     

Phase relations and a15-phase diffusion layer formation in the system Ag-Nb-Ga

Nb₃Ga layers can be synthesized by diffusion from Ag-Ga alloys at 1100°C. This is con-sistent with the hypothesis that the orientation of two-phase tielines in a ternary system, such as Ag-Nb-Ga, play an important role in determining whether superconducting layer formation will occur. Although the superconducting transition onset was 12.3 K, the Nb₃Ga layer growth rates in this system are too slow for practical application. Chemical modification of the phase diagram however does appear to be a feasible approach for pro-moting the diffusion synthesis of A15 phase layers for multifilamentary conductors.