High-temperature phase relations in the ternary Ga-Mn-Ni system

Isothermal sections of the ternary Ga-Mn-Ni phase diagram at 800 and 1000 °C have been investigated for alloys with a manganese content below 70 at.% for 800 °C and a content below 65 at.% at 1000 °C. The high-temperature phase relations among the solid phases have been analyzed with diffusion couples and by energy dispersion x-ray spectroscopy (EDX) on quenched two-phase alloys. For these temperatures, the solidus line was determined from quenched alloys from the solid and liquid two-phase region by EDX analysis and the liquidus line by an overall evaluation of the phases found in the quenched alloys. By powder x-ray diffraction (XRD) measurements, the results for the equilibria among the solid phases were confirmed and the lattice parameters for the martensite formed from the β phase have been determined over a wide range of compositions.     

Phase relations in the Fe-Pu-U ternary system

An isothermal section of the Fe-Pu-U ternary system at 650 °C was assessed in a previous study. In the present study, the predictions of the phase relations in the Fe-Pu-U system to higher and lower temperatures were performed by applying the interaction parameters determined at 650 °C. Differential thermal analysis (DTA) for the Fe-Pu-U alloys was also carried out to confirm the phase relations in the temperature region of 500 to 800 °C. Both results agreed well. On the basis of the predicted ternary phase diagram, the phase relations for a region surrounded by Fe₂Pu, Fe₂U, U, and Pu were described by a reaction scheme and a projection of the liquidus surface.     

Phase relations in the Fe-Pu-U ternary system

An isothermal section of the Fe-Pu-U ternary system at 650 °C was assessed in a previous study. In the present study, the predictions of the phase relations in the Fe-Pu-U system to higher and lower temperatures were performed by applying the interaction parameters determined at 650 °C. Differential thermal analysis (DTA) for the Fe-Pu-U alloys was also carried out to confirm the phase relations in the temperature region of 500 to 800 °C. Both results agreed well. On the basis of the predicted ternary phase diagram, the phase relations for a region surrounded by Fe₂Pu, Fe₂U, U, and Pu were described by a reaction scheme and a projection of the liquidus surface.     

Transformations and phase relations in Nb—Ti—Si ternary system at 1373—1473K

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High-temperature phase equilibria in Ti-Al-Mo system

The phase equilibria in a Ti-Al-Mo system have been investigated at 1473 and 1573 K experimentally and theoretically. Phase equilibria were experimentally investigated by in situ x-ray diffraction and thermal analysis as well as by quenching and diffusion couples. From the results, isothermal sections of this system at these two temperatures were constructed and assessed using Thermo-Calc. A part of the ternary phase diagram of Ti-Al-Mo system has revealed the following features: (1) low solution limits of Mo (a few at.% Mo) in both α (disordered hcp structure) and γ (TiAl: the L1₀ structure) phases, (2) the narrow three-phase region of the α+β (bcc Ti terminal solution) +γ phases, and (3) the role of Mo as a strong “β stabilizer.”     

High-temperature phase equilibria in Ti-Al-Mo system

The phase equilibria in a Ti-Al-Mo system have been investigated at 1473 and 1573 K experimentally and theoretically. Phase equilibria were experimentally investigated by in situ x-ray diffraction and thermal analysis as well as by quenching and diffusion couples. From the results, isothermal sections of this system at these two temperatures were constructed and assessed using Thermo-Calc. A part of the ternary phase diagram of Ti-Al-Mo system has revealed the following features: (1) low solution limits of Mo (a few at.% Mo) in both α (disordered hcp structure) and γ (TiAl: the L1₀ structure) phases, (2) the narrow three-phase region of the α+β (bcc Ti terminal solution) +γ phases, and (3) the role of Mo as a strong “β stabilizer.”     

Experimental investigation of phase equilibria in the Co-W-V ternary system

The phase equilibria in the Co-W-V ternary system were experimentally investigated by optical microscopy (OM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) on the equilibrated alloys. Three isothermal sections of the Co-W-V ternary system at 1100 °C, 1200 °C and 1300 °C were determined, and no ternary compound was found in this system. In addition, a novel phenomena induced by the liquid phase separation in the Co-W-V alloys was firstly discovered, suggesting that a stable liquid miscibility gap exists in the Co-W-V ternary system. The newly determined phase equilibria and firstly discovered phase separation phenomena in the Co-W-V system will provide important information for the development of Co-W based alloys.     

Partial phase diagram of Au-Ag-Dy ternary system

On the basis of Au-Ag, Au-Dy and Ag-Dy binary phase diagrams, the 700 ℃ isothermal section of Au-Ag-Dy ternary system（Dye≤35 %, mole fraction） was established by X-ray diffraction analysis, differential thermal analysis and optical microscopy. It is found that there is a long single-phase region, Au（Ag） or Ag（Au）, along the Au-Ag binary isomorphous system on the gold-silver-rich side of the 700 ℃ isothermal section and between the binary compound Au2Dy and Ag2 Dy there is the all proportional solid solution, （Au2 Dy） or （Ag2 Dy）. It is confirmed that the partial 700 ℃ isothermal section consists of six single-phase regions： solid solution Au（Ag） or Ag （Au）, （Au2 Dy） or （Ag2 Dy）, Au6 Dy, Au51 Dy14, Au3 Dy and Ag51 Dy14 ; nine binary-phase regions; （Au2 Dy） ＋ Au （Ag）, Au6Dy＋ Au（Ag）, Au（Ag） ＋Ag51 Dy14 , Ag51 Dy14 ＋ （Au2Dy）, Au3Dy＋（Au2Dy）, Au3Dy＋ Au51 Dy14, Au51 Dy14＋Au6Dy, Au51 Dy14＋Au（Ag） and Au（Ag） ＋Au3Dy; four ternary regions： Ag51 Dy14＋ （Au2Dy）＋ Au （Ag）, （Au2 Dy） ＋ Au（Ag） ＋ Au3 Dy, Au（Ag） ＋ Au3 Dy＋ Au51 Dy14 and Au51 Dy14＋ Au （Ag）＋ Au6 Dy. No new ternary compound is formed in the gold-silver-rich field（Dy≤35 %） of the Au-Ag-Dy ternary system.     

Experimental determination of the phase equilibria in the Co-Fe-Zr ternary system

The phase equilibria in the Co-Fe-Zr ternary system were investigated by means of optical microscopy (OM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) on equilibrated ternary alloys. Four isothermal sections of the Co-Fe-Zr ternary system at 1300 °C, 1200 °C, 1100 °C and 1000 °C were experimentally established. The experimental results indicate that (1) no ternary compound was found in this system; (2) the solubility of Fe in the liquid phase of the Co-rich corner at 1300 °C is extremely large; (3) the liquid phase in the Zr-rich corner and the (Co,Fe)₂Zr phase form the continuous solid solutions from the Co-Zr side to the Fe-Zr side; (4) the solubility of Zr in the fcc (Co, Fe) phase is extremely small.     

Cu-Ni-Sn三元系相平衡的热力学计算

基于Cu-Ni-Sn三元系的相平衡和热力学的实验信息,采用亚正规溶体模型描述液相和fcc相的Gibbs自由能,为了预测该体系中bcc相的A2-B2有序-无序转变,bcc相的Gibbs自由能采用双亚点阵模型进行描述.利用CALPHAD(相图计算)方法评估了Cu-Ni-Sn三元系各相的热力学参数,计算的富Cu侧相图和热力学性质与实验数据比较一致.并对该三元系中bcc相的A2-B2有序-无序转变及fcc相的溶解度间隙进行了计算.这些计算结果对利用析出强化以及Spinodal分解开发高强度和高导电性的新型Cu基合金的组织设计具有一定的指导意义.     

Solid-liquid phase equilibria at 727 °C in the ternary system Fe-Mg-Si

The solid-liquid phase equilibria in the Fe-Mg-Si ternary system were experimentally investigated at 727 °C by two complementary approaches: reaction to equilibrium of Fe-Mg-Si powder mixtures and growth of reaction zones at the interface of diffusion couples. X-ray powder diffraction, optical metallography (OM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were used to characterize the phases formed in these experiments. It has been shown that except silicon and βFeSi₂, all the compounds and solid solutions stable at 727 °C in the Mg-Si and Fe-Si binary subsystems (Mg₂Si, εFeSi, α₁Fe₃Si, α₂Fe₃Si, and αFe) are in equilibrium at that temperature with a magnesium-rich Mg-Si liquid phase. The liquid simultaneously in equilibrium with FeSi and Mg₂Si contains 3.1±0.2 at.% Si; that involved in the three-phased equilibrium with εFeSi (50 at.% Si) and α₁Fe₃Si (27 at.%Si) contains 1.0±0.05 at.%Si. For lower silicon contents in the liquid, the conjugate solid phases are successively α₁Fe₃Si (DO₃ structure, homogeneity range 27 to 14 at.%Si), α₂Fe₃Si (B2 structure, homogeneity range 14 to 11.5 at.%Si), and αFe (A2 structure, homogeneity range 11.5 to 0 at.% Si). It is however to note that for a silicon content in the liquid as low as about 0.05 at.%, the conjugate solid phase is still quasistoichiometric α₁Fe₃Si with 25 at.% Si.     

The ternary In-Ni-Sb phase diagram in the vicinity of the binary In-Ni system

The central part of the In-Ni phase diagram (0.45 ≤ X_ln ≤ 0.60) was reinvestigated and the adjoining part of the ternary In-Ni-Sb phase diagram was studied experimentally. The investigation included thermal analyses (DTA), x-ray powder diffraction, and microprobe studies (EPMA). The ternary equilibrium phase relations were studied for three isothermal sections at 750,825, and 900 ‡C. Four new invariant ternary phase reactions were identified in the temperature range between 805 and 895 ‡C. A complete reaction scheme was constructed in the corresponding composition range, and the liquidus surface was derived from DTA data. The lattice parameter of the solid solution of Sb in CoSn-type Niln was studied as a function of composition by means of powder diffraction using the Guinier-Huber technique.     

High-temperature oxidation behavior of iridium-based alumina-forming ternary intermetallics

The oxidation behavior of iridium-based intermetallics in the ternary iridium-aluminum-silicon system has been investigated. Additions of up to 20 at. % silicon to iridium-aluminum binary alloys reduce the aluminum concentration necessary for the formation of a protective alumina scale from greater than 55 at.% in the absence of silicon to as low as 20 at.% when 20 at.% silicon is present. Ternary iridium-aluminum-silicon alloys with 30–50 at.% aluminum and 8–10 at.% silicon exhibit parabolic oxidation behavior, and the rate constants are in good agreement with those previously determined for binary iridium-aluminum alloys. The oxidation rate of ternary iridium-aluminum-silicon alloys with 10 at.% silicon and 30–40 at.% aluminum deviates from the parabolic-oxidation behavior for alumina scale growth in the later oxidation stage, presumably due to the formation of a silica inner layer. Thermal cycling of the Ir-50 Al-8Si and Ir-60-Al samples does not result in scale spallation due to the coefficient of thermal expansion match between the alumina scale and intermetallic substrate.     

气相分压对Co-Fe-Sb三元体系相平衡和相稳定性的影响

通过真空条件下Co-Fe-Sb三元体系1 073 K等温截面测定、Co-Fe-Sb三元体系凝聚态的热力学优化评估和气相组分的热力学数据计算,分析气相压力对该体系中二元和三元体系的相平衡和相稳定性的影响。结果表明:随着气相压力减小到一定程度,Co-Sb、Co-Fe、Fe-Sb和Co-Fe-Sb体系中的固相化合物相开始发生挥发分解,出现气液固三相平衡区,计算所得温度—压力曲线图表明每种化合物相都存在一个理论的压力极小值,并对应一个温度,在此压力之上或温度以下,不发生化合物由固相转变成气相的分解,凝聚态相保持与常压下基本相同的相平衡关系。计算结果从热力学上很好地解释了含Sb热电材料在试验研究和材料制备过程中存在的问题,对制备该化合物的工艺设计具有很好的参考作用。     

Experimental investigation and thermodynamic calculation of the phase equilibria in the Co-Nb-Ta ternary system

The isothermal sections of the Co-Nb-Ta ternary system at 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C have been experimentally determined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques on the equilibrated alloys. On the basis of the experimental data investigated in the present work, the phase equilibria in the Co-Nb-Ta system has been thermodynamically assessed by using CALPHAD (CALculation of PHAse Diagrams) method, and a consistent set of the thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.     

Calculation of phase equilibria for the ternary system by the grand potential method

The relationships among the grand potential,G, the chemical potential, μ_i, and the effective chemical potential, μ_i, are geometrically demonstrated. An important equation concerning the relationship between the effective chemical potential, μ_i, and the molar free energy, F_m, was deduced. Use of the grand potential method enables calculation of the phase equilibria for the miscibility gap and different crystal structures in the ternary system.     

Calculation of phase equilibria for the ternary system by the grand potential method

The relationships among the grand potential,G, the chemical potential, μ_i, and the effective chemical potential, μ_i, are geometrically demonstrated. An important equation concerning the relationship between the effective chemical potential, μ_i, and the molar free energy, F_m, was deduced. Use of the grand potential method enables calculation of the phase equilibria for the miscibility gap and different crystal structures in the ternary system.     

Experimental determination of phase equilibrium in the Fe–Co–Sb ternary system

Phase stability and phase transformation were studied in the Fe–Co–Sb ternary system for the three sections: CoSb–Fe_0.56Sb_0.44, 30 at.% of Sb and 75 at.% of Sb. In the first section, we find a continuous solid solution without any secondary phase. The unit cell volume increases as a function of X_Fe/(X_Fe + X_Co). At 30 at.% of Sb, the B8 and the bcc-A₂ phases are obtained across the whole Fe–Co section. On the CoSb₃ side (75 at.% of Sb), Fe atoms cannot completely substitute for Co atoms in the skutterudite structure. Below 5 at.% of substitution of Fe for Co in CoSb₃, only the D0₂ phase is present while for high concentration of Fe, marcasite and Sb phases coexist.