Phase equilibria in Fe-Cu-X (X: Co, Cr, Si, V) ternary systems

Phase equilibria on the Fe-Cu side in the Fe-Cu-X (X: Co, Cr, Si, V) system were experimentally determined over the temperature range of 1073–1273 K. Based on the present results and previous works, the thermodynamic assessments of the phase equilibria in the Fe-Cu-X system were evaluated using the Calculation of Phase Diagram (CALPHAD) method. The Gibbs energies (G) of the bcc, fcc, and liquid phases are described by the subregular solution model, and a set of thermodynamic parameters enable us to calculate various isothermal and vertical sections and the miscibility gaps of the solid and liquid phases.     

Phase equilibria of Co3 V

In situ neutron diffraction experiments were performed over a wide range of temperatures on the alloy Co₃V. These experiments showed that theL1₃ region of the phase diagram does not exist. The ob-served Ll₂ phase appears to be a metastable state that can be obtained in quenched alloys. The hP24-fcc phase boundary was estimated to be 1045 ?.     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: V, Nb and Ta) ternary systems

A systematic investigation was carried out to determine both liquidus and solidus surfaces of the Ni-solid solution (γ) in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis (DTA) technique. Each of the Group V elements of the periodic table, V, Nb, and Ta, was chosen as a ternary additive X in the present study. The γ-solvus was also taken into account in determining a temperature range for a solid solution treatment above the γ-solvus, i.e., “the window,” as well as the maximum solubility limit of γ-Ni solid solution.     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: V, Nb and Ta) ternary systems

A systematic investigation was carried out to determine both liquidus and solidus surfaces of the Ni-solid solution (γ) in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis (DTA) technique. Each of the Group V elements of the periodic table, V, Nb, and Ta, was chosen as a ternary additive X in the present study. The γ-solvus was also taken into account in determining a temperature range for a solid solution treatment above the γ-solvus, i.e., “the window,” as well as the maximum solubility limit of γ-Ni solid solution.     

Phase equilibria and microstructures in the Fe–Si–Cr–Ti system

Having known that the (A2+D0₃) two-phase microstructure is obtained at below 873 K in the ternary Fe–Si–Cr alloy with 12–15 at.%Si at constant 10 at.%Cr, the effect of Ti additions to the ternary system on the possibility of having Huesler L2₁ phase in addition to D0₃ phase is examined. Microstructures of the quaternary Fe–10 and 12 at.%Si–10 at.%Cr–0.5 and 1 at.%Ti alloys are investigated by transmission electron microscopy through which identification and morphology of the phases precipitating within the A2 matrix are examined. It is found that the Ti addition to the ternary Fe–Si–Cr system provides (A2+L2₁) two-phase and/or (A2+D0₃+L2₁) three-phase regions. Morphology of the L2₁ phase is spherical or cuboidal, while that of D0₃ precipitates is rod-like, a difference which may be explained by the difference in magnitude of the misfit between the precipitate and the A2 matrix caused by the difference in partitioning of Ti to each phase.     

NiAl-based polyphase in situ composites in the NiAl---Ta---X (X = Cr, Mo, or V) systems

Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni---Al---Ta---X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl---NiAlTa---(Mo, Ta), NiAl---(Cr, Al) NiTa---Cr, and the NiAl---NiAlTa---V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100–1400 K. Of the ternary eutectics, the one in the NiAl---Ta---Cr system was found to be the most promising. The fracture toughness of the NiAl---(Cr, Al)NiTa---Cr eutectic was intermediate between the values of the NiAl---NiAlTa eutectic and the NiAl---Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl---Cr eutectic.     

Ni-Al-Sn三元系相平衡的实验研究

采用电子探针显微分析和X-ray衍射分析方法实验研究了Ni-Al-Sn三元体系在800°C和1000°C时的相平衡。结果表明：(1) Ni-Al-Sn三元体系在800°C和1000°C时均未发现三元化合物;(2) Ni-Al侧包含NiAl、Ni3Al、Al3Ni和Al3Ni2四个化合物,其中800°C时,Sn在NiAl和Ni3Al中的固溶度在分别为3.1和14.7 at.%,在1000°C时分别为3.0和8.0 at.%。而Sn在Al3Ni和Al3Ni2相中几乎没有固溶度;(3) Ni-Sn侧包含Ni3Sn(r)、Ni3Sn(h)和Ni3Sn2(h)三个化合物相。800°C时,Ni3Sn(r)相的固溶度为4.2 at.%,1000°C时,Ni3Sn(r)相转变为Ni3Sn(h)相,拥有5.5 at.% 的固溶度。另外,800°C时,Al在Ni3Sn2(h)相中的固溶度为8.4 at.%,1000°C时为12.1 at.%;(4) Ni-Al-Sn三元体系Al-Sn侧为相互贯通的液相区域,实验测得的Ni在Al-Sn侧的溶解度约为1 at.%。     

Co-Cu-Zn三元系相平衡的实验研究

本实验通过采用电子探针显微分析和X-ray衍射分析方法实验研究了Co-Cu-Zn三元体系在800°C和1000°C时的相平衡。在这两个等温截面中均未发现三元化合物。在800°C等温截面,Co在β-CuZn相中的固溶度为32.36%,Cu在β1-CoZn相中的固溶度为5.28%。除此之外,γ-Co5Zn21和γ-Cu5Zn8具有相同的晶体结构,因此,它们之间形成了一个贯穿连续固溶体相。1000°C的等温截面中,β-CuZn相、β1-CoZn相、γ-Co5Zn21相、γ-Cu5Zn8相都消失了。随着温度从800°C上升到1000°C,液相区域增大。     

A priori calculations of adsorption equilibria in ternary systems

The article describes the procedure for a priori calculations of the equilibrium properties of the adsorption of ternary solutions based on experimental data for corresponding binary solutions. The calculation is based on a method developed previously by the authors that facilitates the highly accurate determination of the equilibrium activities of components in ternary volumetric solutions as a function of the predetermined composition of an adsorbed solution.     

C—Fe—X（X=Mn,Si,Cr,Ni）熔体中组元活度的解析

将过剩自由能表达为组元的多项式函数。以该体系液相区边界条条件为基础,用拟合法确定碳偏mole自由能表达式中的参数,然后,用“I—D”法给出组元X的活度系数,此法可以确定各C—Fe—X系整个液相区中任一组元的活度,解析结果与文献上的试验结果吻合得很好。     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: Ti, Zr, and Hf) ternary systems

A systematic investigation has been carried out to determine both the γ liquidus and solidus surfaces above the Ni solid solution in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis. Each of the group IV elements in the periodic table, Ti, Zr, and Hf, was chosen as the ternary additive X in the present study. As a basis, γ liquidus and solidus temperatures in the Ni-Al binary system were reinvestigated and evaluated. The γ solvus was also taken into account to determine a temperature range for a solid-solution treatment above the γ solvus, generally called “the window,” as well as the maximum solubility limit of γNi solid solution.     

Phase equilibria in the Co-Ti portion of the Co-Al-Ti ternary system

Phase equilibria of 900, 1000, and 1100 °C in the Co-Ti portion of the Co-Al-Ti system were mainly determined by energy dispersion x-ray spectroscopy. On the Ti-Al side, the β-Ti (A2) phase region is extended by the addition of Co and the β-Ti + AlTi₃ (D0₁₉) two-phase region appears in the ternary equilibrium, while the AlTi (L1₀), AlTi₃, and β-Ti phases show very low solubility of Co. It was found that the two ternary intermetallic compounds, Co₂AlTi (L2₁) and CoAl₂Ti (D8 _a ), exist over a wide solubility range along the CoAl(B2)-CoTi (B2) and CoAl₃-CoTi₃ sections, respectively. The ordering transition and the phase separation due to ordering of the β-Ti, CoAl, or CoTi and Co₂AlTi phases fundamentally possessing the bcc structure are also discussed.     

Phase equilibria in the Co-Ti portion of the Co-Al-Ti ternary system

Phase equilibria of 900, 1000, and 1100 °C in the Co-Ti portion of the Co-Al-Ti system were mainly determined by energy dispersion x-ray spectroscopy. On the Ti-Al side, the β-Ti (A2) phase region is extended by the addition of Co and the β-Ti + AlTi₃ (D0₁₉) two-phase region appears in the ternary equilibrium, while the AlTi (L1₀), AlTi₃, and β-Ti phases show very low solubility of Co. It was found that the two ternary intermetallic compounds, Co₂AlTi (L2₁) and CoAl₂Ti (D8 _a ), exist over a wide solubility range along the CoAl(B2)-CoTi (B2) and CoAl₃-CoTi₃ sections, respectively. The ordering transition and the phase separation due to ordering of the β-Ti, CoAl, or CoTi and Co₂AlTi phases fundamentally possessing the bcc structure are also discussed.     

Investigation of microcrystalline NiAl-based alloys with high-temperature thermoelastic martensitic transformation: I. Resistometry of the Ni-Al and Ni-Al-X (X = Co, Si, or Cr) alloys

Six microcrystalline alloys rapidly quenched from the melt (Ni₆₄Al₃₆, Ni₆₅Al₃₅, Ni₆₆Al₃₄, Ni₅₆Al₃₄Co₁₀, Ni₆₄Al₃₂Si₂, and Ni₆₄Al₃₂Cr₄, at %) have been investigated using polythermal and isothermal resistometry with a subsequent microstructural analysis. The absence of reversibility of the thermoelastic martensitic transformation for all these alloys (except for Ni₆₄Al₃₆ and partly Ni₅₆Al₃₄Co₁₀), the reason for which is a strong tendency to a diffusive decomposition of the “fresh” (as-quenched) martensite of these alloys has been revealed. New regimes of stabilizing annealing that enable application of high-nickel alloys based on nickel-aluminum martensite as functional materials with a high-temperature shape-memory effect have been suggested.     

Thermodynamic modeling of the Pd-X (X=Ag, Co, Fe, Ni) systems

A set of self-consistent thermodynamic model parameters is presented to describe the phase equilibria of the Ag-Pd, Co-Pd, Fe-Pd, and Ni-Pd systems. In most cases, the calculated values using the optimized model parameters agree very well with the experimental data. The FePd and FePd₃ phases with large homogeneity ranges are described by the compound energy formalism. At present, insufficient thermodynamic data are available for these two phases. Therefore, experimental data on the heat of formation and/or the first-principle calculation of cohesive energies will be very useful for further refinement of thermodynamic parameters of FePd and FePd₃ phases.     

EVALUATION OF COMPONENT ACTIVITIES IN THE MOLTEN C_Fe-X(X=Si,Mn,Cr,Ni)SYSTEM

Expressing the excess partial molar free energies and integral excess free energy as poly-nome of the composition,then the parameters in the expression of excess partial molarfree energy of C were evaluated based on:the excess partial free energy of C in C-Fe bi-nary alloy:the integral excess free energy of Fe-X binary alloy:the C saturation curveand the iso-activity curve of C (α_c=0.025) in the ternary system.Then the activitycoefficient of X was evaluated with the so-called “I-D” method,by which the componentactivities of every element in the whole molten ternary alloy can be evaluated,and theresults are in good agreement with literature data based on experiment.     

Phase stability of the X2AlTi (X: Fe,Co, Ni and Cu) Heusler and B2-type intermetallic compounds

Ordering and phase separation between the B2 and L21 phases in the X2AlTi (X: Fe, Co, Ni, Cu) intermetallic compounds were investigated. The B2/L21 continuous ordering was determined using the diffusion couple technique in the temperature range of 1273–1573 K. It was found that the substitution of Co for Fe results in raising the B2/L21 ordering temperature and that of Cu for Ni brings about widening of the B2+L21 two-phase region on both the NiAl and NiTi sides. It is shown that the maximum temperatures of B2/L21 order–disorder transition (TcB2/L21max), the tricritical temperatures (TtB2/L21) and the phase boundaries of the miscibility gap between the B2 and L21 phases in the XAl–XTi pseudobinary systems can be well described by the 3d+4s electron concentration of the elements occupying the X site. On the basis of this finding, the phase stability and the interchange energies between Al and Ti in the next nearest neighbors of X–Al–Ti (X: Ti, V, Cr, Mn, Fe, Co, Ni and Cu) system are discussed.