X-ray studies on phase equilibria in {Tm, Lu} - W - B ternary systems at 1070 K

Isothermal sections at 1070 K have been constructed by x-ray diffraction applied to the phase diagrams in the Tm - W - B and Lu - W - B systems. The solubility of “WB₂” in TmB₂ is low, while that in LuB₂ attains 0.15 molar fraction (lattice parameters of the (Lu, W) B₂ phase with a limiting composition and having the AlB₂ structure a=0.31772(6), c=0.35804(9) nm). The distinct boride reported previously Tm₃WB₇ is confirmed (Er₃CrB₇ structure type). New ternary compounds have been identified and examined by powder method (DRON-3M diffractometer): TmWB₄ (space group Pbam, structure type YCrB₄, a=0.59989(2), b=1.15866(4), c=0.35821(1) nm, N_hkl=157, R=0.0796) and Lu₂WB₆ (Pbam, structure type Y₂ReB₆, a=0.91339(4), b=1.14865(5), c=0.35124(2) nm, N_hkl=408, R=0.0981). Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 43–48, May–June, 2000.     

Phase Equilibria in the Nd ― Re ― B System

XRD has been applied to component interaction in the Nd ― Re ― B system. Isothermal sections have been constructed for the phase diagram at 600°C (a region >33 at.% boron) and 800°C (>33 at.% boron). It is confirmed that it contains the previously known borides Nd₂Re₃B₆ (Pr₂Re₃B₆ structure type) and Nd₈Re_{13 − x} B₁₂ (Pr₈Re_{13 − x} B₁₂ structure type). Two new ternary compounds are reported: ∼NdRe₄B₄ considered to have a tetragonal incommensurate structure and ∼Nd₅Re₂B₆, whose structure is unknown.

     

Phase Equilibria in the Nd ― Re ― B System

Powder Metallurgy and Metal Ceramics - XRD has been applied to component interaction in the Nd ― Re ― B system. Isothermal sections have been constructed for the phase diagram at...     

Fe-Cr-Ni-C四元系奥氏体与碳化物之间的相平衡计算

将Bjorn Uhrenius描述Fe-C基三元合金体系热力学性质的亚点阵模型扩展后应用于Fe-C基四元合金体系,给出了自由能函数关系表达式,并且在Biorn Uhrc-nius对Fe-Cr-C系热力学平衡计算的基础上,再结合Nishizawa对于Cr-Ni二元系给出的交互作用参数,对Fe-Cr-Ni-C系中固溶体和碳化物的两相平衡进行了计算求解。     

Phase equilibria in the system Al-Rh

Methods of differential thermal analysis, x-ray diffraction, microstructural analysis and electron probe microanalysis are used to study alloys of the Al-Rh system over the whole concentration range. It is established that the phase of equiatomic composition AlRh melts congruently at 2060°C and it has an extended range of homogeneity (45.1–54.2 at.% Rh). The solubility of aluminum in rhodium reaches 9 at.%, decreasing to 6 at.% at 850°C. Coordinates are determined for the eutectic point l ⇆ AlRh + 〈Rh〉 as 70 at.% Rh and 1715°C. The existence of intermediate phases, their crystal structure, and also the method of forming phases in the field of composition rich in aluminum given in publications are confirmed. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 48–56, May–June, 2006.     

Phase Equilibria in the Ni - Sc - Ti System in the Region TiNi - Ni - Sc1.13Ni At 900°C

Physicochemical analysis methods have been applied to TiNi - Ni - Sc_1.13Ni alloys at 900°C. It is shown that the phase interactions under these conditions are unaltered by comparison with those at subsolidus temperatures. The phase based on TiNi₃, which is the most thermally and thermodynamically stable, is in equilibrium with all the other phases in the TiNi - Ni - Sc_1.13Ni subsystem. The solubilities of the components in the phases based on Ti_{50– x} NiSc_x, TiNi₃, and the Laves phase are reduced at 900°C. The temperature of the polymorphic transformation in the phase based on ScNi₅ is raised by the dissolution of titanium in it to 930°C. An isothermal section is constructed of the phase diagram for the TiNi - Ni - Sc_1.13Ni subsystem together with two polysections.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 39–46, January–February, 2005.     

Phase Equilibria in the Lu ― V ― B System and the Structure of the New Boride Lu1.34V1.66B6

X-ray diffraction data have been used to construct the 1070 K isothermal section of the Lu V B phase diagram. The solubility of VB₂ in LuB₂ attains 5 at.% (lattice parameters of the (Lu, V)B₂ phase of the limiting composition with the AlB₂ structure are a = 0.3238(1), c = 0.3689(1) nm). A new ternary boride has been discovered, Lu_1.34V_1.66B₆, which belongs to the Y₂ReB₆ structure type (space group Pbam, a = 0.8947(8), b = 1.1273(7), c = 0.3381(2) nm, F _hkl > 4(F), 2thetav;_max = 72.76°, N _hkl = 379, R _F = 0.0617, R _w = 0.0653) and is characterized by a statistical distribution of the Lu and V atoms in one of the structure positions.     

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.     

Thermodynamics of Liquid Alloys and Metastable Phase Transformations in the Copper - Titanium System

We have used solution calorimetry at temperatures of 1573 K and 1873 K over broad concentration ranges to study the mixing enthalpy of Cu - Ti liquid alloys. The molar mixing enthalpies of the system are significant negative values. We have established the temperature dependence of the molar mixing enthalpies of the system: there is an increase in their exothermicity as the temperature is lowered. The significant negative mixing enthalpies of the system allow us to conclude that the chemical bonds are localized in the studied melts and consequently associates form. We tested this conclusion within ideal associated solution theory, which describes well the results obtained with a set of CuTi and CuTi₂ associates. Using the model obtained, we have calculated the excess thermodynamic functions of mixing (enthalpy, Gibbs free energy, heat capacity) for the liquid alloys. We estimated the Gibbs energies of fcc, bcc, and hcp solutions in the system by the CALPHAD method, using data from the initial sections of the phase diagrams and from the corresponding thermodynamic data. We have calculated the metastable phase equilibria between the limiting solid solutions and the liquid or supercooled liquid phase. It was shown that for the supercooled liquid and the amorphous phase, a broad concentration range of relative thermodynamic stability can be obtained. The concentration range of amorphization of Cu - Ti melts corresponds to the position of the metastable liquidus line and the T₀ line at temperatures close to the temperature range of amorphous solidification. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 67–80, May–June, 2005.     

The Solidus Surface in the Ti ― Ni ― Hf System in the Ti ― TiNi ― HfNi ― Hf Region

Studies have been done on the phase equilibria at subsolidus temperatures in the Ti TiNi HfNi Hf region of the Ti Ni Hf ternary system. The phases based on binary compounds and solid solutions of these components are accompanied in the equilibria by a phase based on an equiatomic ternary compound. This new phase belongs to the family of Laves phases and has a hexagonal crystal structure of MgZn₂ type. The solidus surface in the Ti TiNi HfNi Hf subsystem consists of the surface of the ternary phase alone, the surfaces of the six solid solutions based on the components and binary intermediate phases, the planes of five conode triangles, and the corresponding lineated surfaces.     

Phase Constitution in Mixed Gd_2O_3 and B_4C by Sintering at High Temperature

The phase constitution in mixed Gd2O3 and B4C by sintering in graphite tube furnace at the temperature of 100～1489 ℃ in argon atmosphere was studied by means of XRD and TG-DTA. The results show that the impurity C reacts with O in the B4C at the temperature of 367～458 ℃. When the temperature is 800 ℃, Gd2O3 reacts with B4C, and the reaction products include GdB6, GdB4, GdBO3, GdBC and B. GdBC changes into GdB4 at 1200 ℃. When the temperature is 1470 ℃, GdB6 is obtained by the reaction of GdB4 with elemental B. The content of GdB6 is increasing with the prolonging time.     

Non-stoichiometry Effects and Phase Equilibria in the Uranium-Carbon-Nitrogen Ternary System

Metallurgical and Materials Transactions A - Uranium carbonitride—a solid solution of stoichiometric UC and UN compounds—is considered as a potential nuclear fuel, and is only one of...     

Phase Equilibria and Interstitial Effects in the Ti-V-Mo Alloy System

The stability of theβ phase in the Ti-V, Ti-Mo, and Ti-V-Mo alloy systems was investi-gated, and theβ/α + β phase boundaries in these systems were determined in the range 300 to 600° C. The results indicate that Mo is more potent than V in stabilizing theβ phase with respect to α phase formation and in retarding the β → α reaction kinetics. It is shown that increasing the oxygen concentration in the alloys tends to enhance α phase formation in Mo-lean alloys (Mo contents < 15 wt pct), whereas it leads to the formation of an oxide phase in Mo-rich alloys (Mo contents ≥15 wt pct). Formerly Research Assistant, Department of Materials Science, University of Southern California     

Study of the Process of Phase Formation during Detonation Spraying of Composite Powders of the FeTi - SiC System

We have studied the dependences of the structure, phase composition, and properties of coatings obtained by detonation spraying of powders of the system 77 mass% FeTi - 23 mass% SiC on the method by which they are prepared. We have established substantial differences in morphology and composition for coatings sprayed from conglomerated and presintered powders. We have shown that the process of formation of new phases occurs more rapidly when spraying conglomerated powders.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 67–73, January–February, 2005.     

Mg_(91.4)Zn_(7.2)Y_(1.4)合金中的相变及相平衡

采用热分析以及合金平衡组织结构分析,对Mg-Zn-Y系Mg_(91.4)Zn_(7.2)Y_(1.4)合金中的相变及其相关相平衡进行了研究.结果表明,Mg_(91.4)Zn_(7.2)Y_(1.4)合金在440℃时处于α-Mg固溶体和准晶I的两相平衡;450℃时处于α-Mg固溶体、液相Liq和三元化合物W的三相平衡.Mg_(91.4)Zn_(7.2)Y_(1.4)合金在446.8℃时发生了I+α-Mg→Liq+W四相包共晶转变.温度超过477.3℃,Mg_(91.4)Zn_(7.2)Y_(1.4)合金中W相不再稳态存在,500℃时合金处于α-Mg和液相两相平衡.     

Phase Equilibria in the Be-Al-Fe System Using High-Energy Ion Beams: II

Ion beam methods have been used in a study of the beryllium rich region of the beryl-lium-aluminum-iron phase diagram. Tailored alloys formed by ion-implanting aluminum and iron into beryllium were annealed, and their evolution with time was followed by ion backscattering analysis. In this way, the maximum and minimum aluminum to iron atomic ratios in the ternary phase of nominal composition AlFeBe₄ were determined in the temperature range 773 to 1073 K; these ratios are 1.4 ±0.1 and 0.93 ±0.15, respec-tively, with any temperature dependence being less than the experimental uncertainty. In addition, the solubilities of aluminum and iron in beryllium were measured for the three-phase condition where α-Be, AlFeBe₄, and FeBe₁₁ coexist. When combined with previous ion beam results for the boundaries about the α-Be phase on the phase diagram, these data provide a detailed picture of the beryllium-rich region of the beryllium-aluminum-iron phase diagram.