Phase diagram of the Al2O3-ZrO2-Sm2O3 system. III. Solidus surface and phase equilibria in alloy crystallization

A projection has been constructed for the solidus surface in the Al₂O₃-ZrO₂-Sm₂O₃ phase diagram on the plane of the concentration triangle, which consists of seven isothermal three-phase fields corresponding to two nonvariant equilibria of eutectic type and five nonvariant equilibria of peritectic type, and also eight lineated surfaces for the end of crystallization of the binary eutectics. The highest temperature on the solidus surface is 2710°C, the melting point of pure ZrO₂, while the lowest is 1680°C, the temperature of the triple eutectic Al + F + SA. No ternary phases or appreciable regions of solid solutions based on the components and the binary compounds are observed. Data on the bounding binary systems, the liquidus and solidus surfaces have been used to construct the phase-equilibrium (melting) diagram together with a reaction scheme for the equilibrium crystallization of alloys in the Al₂O₃-ZrO₂-Sm₂O₃ system. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 56–64, May–June, 2006.     

Phase diagram of the Al2O3-ZrO2-Er2O3 system. II. Phase diagram liqiudus surface

The liquidus surface for the Al₂O₃-ZrO₂-Er₂O₃ phase diagram is projected for the first time onto a concentration triangle. No ternary compounds are found in the system. The liquidus surface is completed by eight primary crystallization fields. Four four-phase nonvariant eutectic equilibria, one four-phase nonvariant transformation equilibrium, and three three-phase nonvariant eutectic equilibria are found in the system. Since ZrO₂ interacts with other phases eutectically, the unique properties of ZrO₂-based T-and F-solid solutions can be combined with the properties of other phases of the ternary system in composite materials. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 64–71, 2007.     

Phase diagram of the ZrO2-Y2O3-Sm2O3 system in the melting-point region

A polynomial method has been used to construct a model for the liquidus surface in the ZrO₂-Y₂O₃-Sm₂O₃ phase diagram; that surface is made up of four fields of primary crystallization for the following phases: solid solutions based on cubic (C) and hexagonal (H) Y₂O₃, cubic ZrO₂ with a structure of fluorite type F, and high-temperature cubic La₂O₃ (X). The ternary system has two nonvariant four-phase equilibria of incongruent type. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(450), pp. 60–67, July–August, 2006.     

Phase diagram of the Al2O3-ZrO2-Er2O3 system. III. Solidus surface and phase equilibria in alloy crystallization

The solidus surface for the Al₂O₃-ZrO₂-Er₂O₃ phase is projected for the first time onto the concentration triangle. It consists of five isothermal three-phase fields that correspond to four invariant eutectic equilibria, one invariant transformation equilibrium, and six ruled binary eutectic solidus surfaces. The highest solidus temperature in the system is 2710 °C, which is the melting point of pure ZrO₂, and the lowest is 1720°C, which is the melting point of the ternary eutectic AL + F + Er₃A₅. Neither ternary phases nor visible solid solution areas based on components and binary compounds are found in the system. Based on the data on bounding binary systems, liquidus, and solidus surfaces, the phase equilibrium diagram and reaction scheme for equilibrium crystallization of Al₂O₃-ZrO₂-Er₂O₃ alloys are constructed. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 74–83, 2007.     

Al2O3-ZrO2-Yb2O3 phase diagram. II. Liquidus surface

The liquidus surface for the Al₂O₃-ZrO₂-Yb₂O₃ phase diagram is constructed for the first time. No ternary compounds are found in the system. The liquidus surface is completed by seven primary crystallization fields. Two four-phase invariant eutectic equilibria, two four-phase invariant transition equilibria, and one three-phase invariant eutectic equilibrium are found in the ternary system. Since ZrO₂ interacts with other phases eutectically, composite materials can combine the unique properties of ZrO₂-based T-and F-phases with the properties of other phases of the Al₂O₃-ZrO₂-Yb₂O₃ system.     

Phase diagram of the Al2O3-ZrO2-Sm2O3 system. I. Triangulation and isothermal sections at 1250 and 1650°C

Isothermal sections at 1250 and 1650 °C have been constructed for the Al₂O₃-ZrO₂-Sm₂O₃ phase diagram, and phase equilibria at those temperatures have been demonstrated. No ternary compounds are found and nor are areas of solid solutions based on components and binary compounds in the system. Partially quasibinary sections Al₂O₃-F, SmAlO₃-(66.7% ZrO₂ · 33.3% Sm₂O₃), and Sm₄Al₂O₉-F have been detected, which triangulate the ternary system, and a demonstration is given of the mechanism for penetration of a phase Sm₂Zr₂O₇ with the structure of the pyrochlore into the middle of the Al₂O₃-ZrO₂-Sm₂O₃ system.     

Phase diagram of the Al2O3-ZrO2-Er2O3 system. iv. vertical sections

For better presentation of the Al₂O₃-ZrO₂-Er₂O₃ phase diagram over a wide temperature and concentration ranges, three vertical sections are plotted to show interactions in the ternary system. The Er₂O₃-(50 mole% Al₂O₃ · 50 mole% ZrO₂) bisector shows the Er₂O₃-enriched region of the Al₂O₃-ZrO₂-Er₂O₃ phase diagram and explains the mechanism of Er₂O₃ phase transformations X ? H ? A ? B. The 15 mole% ZrO₂ (15Z) isopleth shows the Al₂O₃-ZrO₂-Er₂O₃ structure within the region adjacent to the Al₂O₃-Er₂O₃ binary bounding system. The ZrO₂-ErAlO₃ bisector depicts the ternary system in the ZrO₂-enriched region. The vertical sections intersect each of the three triangulating sections of the ternary system and demonstrate the width variation in their two-phase regions.     

Phase diagram for the system CaO-Al2O3-ZrO2

Phase equilibria in the system CaO-Al₂O₃-ZrO₂ were studied to optimize nozzle composition for tundishes that are used in continuous casters of steel, by identifying the composition that minimizes clogging. Mixtures of CaO, Al₂O₃, and ZrO₂ with various compositions were equilibrated at 1873 and 1773 K and then quenched into water. X-ray diffraction analysis was used for phase identification, and electron probe microanalysis was employed to measure chemical compositions. On the basis of these and previous results, the eutectic and peritectic lines have been estimated. Based on the phase diagram, the optimal nozzle composition is CaO-saturated CaZrO₃.     

Phase diagram of the Al2O3-ZrO2-Er2O3 system. I. Isothermal sections at 1250 and 1650°C

Isothermal sections at 1250 and 1650 °C have been constructed for the Al₂O₃-ZrO₂-Er₂O₃ phase diagram. Phase equilibria at these temperatures have been identified. It is not found that there are any ternary compounds or noticeable regions of solid solutions based on the components or binary compounds. Conditionally quasibinary sections have been identified: Er₃A₅-F, ErA-F, and Er₂A-F, which triangulate the Al₂O₃-ZrO₂-Er₂O₃ ternary system.     

Phase equilibria in the system HfO2-Y2O3-La2O3 AT 1900°C

We have used x-ray phase analysis, electron-probe microanalysis, petrography, and electron microscopy on annealed specimens to study phase equilibria in the ternary system HfO₂-Y₂O₃-La₂O₃ at 1900 °C over the entire concentration range. We have plotted the isothermal cross section of the phase diagram for this system at the indicated temperature. We found 23 phase regions. A typical feature of the system is formation of solid solutions based on different crystal modifications of the starting components (A-and H-La₂O₃, C-Y₂O₃, T-and F-HfO₂) and also the compounds La₂Hf₂O₇, LaYO₃. We did not observe new phases in the system. The nature of the phase equilibria in the system is consistent with the high relative thermodynamic stability of lanthanum hafnate (ΔH °La₂Hf₂O₇ ≈ 100 kJ/mole) compared with LaYO₃. We established that adding a third component extends the thermal stability region for the ordered phase of LaYO₃ toward higher temperatures. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 73–87, January–February, 2006.     

Effect of Oxygen Partial Pressure on Phase Equilibria and Liquidus in CaO-Al2O3-FeOx System

 A high temperature equilibration experiment was carried out to investigate the effect of oxygen partial pressure on the phase equilibria and liquidus in CaO-Al2O3-FeOx system with the intermediate oxygen partial pressures of 10.13 Pa and 1.01×10-3 Pa. The equilibrated phases and their compositions of the quenched samples were analyzed by using SEM/EPMA (Scanning Electron Microscope/Electron Probe Micro-Analysis) and XRD (X-Ray Diffraction). The phase equilibrium results include two cases, the two-phase coexistence and the three-phase coexistence in the high Al2O3 region with oxygen partial pressure of either 10.13 Pa or 1.01×10-3 Pa. Effects of oxygen partial pressure and temperature on the liquidus along the primary phase fields of CaO·Al2O3 and CaO·2Al2O3 were notable. With the decrease of oxygen partial pressure, the liquid area expands and the liquidus of CaO·Al2O3 and CaO·2Al2O3 primary fields moves to the Al2O3-FeOx region. On the other hand, the liquid area of CaO-Al2O3-FeOx system extends extremely to the high Al2O3 region with the temperature increasing from 1400 to 1500 ℃, especially at lower oxygen partial pressure. The present experiment results are in good agreement with the calculated ones by FactSage.     

Polythermal sections of the Al2O3-ZrO2-Y2O3 phase diagram

Polythermal sections of the Al₂O₃-ZrO₂-Y₂O₃ phase diagram confirm that the system is quasibinary and enable one to give a complete phase diagram for the system. The ternary eutectic Al₂O₃ + ZrO₂ (solid solution) + Y₃Al₅O₁₂ has the lowest melting point in the system, whose temperature is 1715°C. No single-phase regions for the ternary solid solutions have been identified, which indicates that Al₂O₃ is not soluble in solid solutions based on F-ZrO₂ and C-Y₂O₃. This gives theoretical evidence for the scope for making new ceramics in this ternary system, which may have a high level of mechanical characteristics.     

Al2O3-ZrO2-Yb2O3 phase diagram. III. Solidus surface and phase equilibria in alloy solidification

The solidus surface for the Al₂O₃-ZrO₂-Yb₂O₃ phase diagram is plotted onto the concentration triangle for the first time. It consists of four isothermal three-phase fields that correspond to two invariant eutectic equilibria and two invariant peritectic equilibria. The solidus surface also includes five ruled surfaces representing the end of crystallization in binary eutectics. The highest solidus temperature in the system is 2710 °C, which is the melting temperature for pure ZrO₂, while the lowest temperature is 1765 °C, which is the melting temperature for the AL+F+Yb₃A₅ ternary eutectic. No ternary compounds or noticeable areas of solid solutions based on components and binary compounds are found in the ternary system. The phase equilibrium diagram and reaction scheme for the equilibrium crystallization of Al₂O₃-ZrO₂-Yb₂O₃ alloys are plotted using data on bounding binary systems and liquidus and solidus surfaces.     

Solidus Surface and Phase Equilibria in Al2O3 ― ZrO2 ― La2O3 Alloy Crystallization

The projection of the solidus surface in the phase diagram for the Al₂O₃ ZrO₂ La₂O₃ system on the plane of a concentration triangle has been constructed, which consists of seven isothermal three-phase fields corresponding to three nonvariant equilibria of eutectic type and four nonvariant equilibria of peritectic type, as well as four lineated surfaces for the end of crystallization in the binary eutectics. The highest temperature on the solidus surface is 2710°C, and the lowest is 1665°C. No ternary phases and appreciable areas of solid solution are observed. Data on the bounding binary systems, liquidus and solidus surfaces have been used to construct the phase-equilibrium diagram together with a scheme for the reactions in equilibrium crystallization in the Al₂O₃ ZrO₂ La₂O₃ system.