Densities of solid aluminum-magnesium (Al-Mg) alloys

Densities of solid Al and Al-Mg alloys were measured by the dilatometric method for seven compositions at mole fractions of magnesium: 0.015, 0.05, 0.1, 0.125, 0.15, 0.20, and 0.25. A curvilinear dependence of density on temperature (room temperature up to 800 K) was observed for all investigated alloys. Results are described by polynomials of the second degree. The molar volumes of Al-Mg alloys were calculated from the density measurements. It has been found that the densities of solid Al-Mg alloys show negative deviations from linearity and the molar volumes exhibit positive deviations from ideal behavior for all samples in the experimental concentration range. The density of the β(Al₃Mg₂) phase along the (α(Al) + β)/β boundary was calculated and is described by a temperature-dependent polynomial.     

Densities of solid aluminum-magnesium (Al-Mg) alloys

Densities of solid Al and Al-Mg alloys were measured by the dilatometric method for seven compositions at mole fractions of magnesium: 0.015, 0.05, 0.1, 0.125, 0.15, 0.20, and 0.25. A curvilinear dependence of density on temperature (room temperature up to 800 K) was observed for all investigated alloys. Results are described by polynomials of the second degree. The molar volumes of Al-Mg alloys were calculated from the density measurements. It has been found that the densities of solid Al-Mg alloys show negative deviations from linearity and the molar volumes exhibit positive deviations from ideal behavior for all samples in the experimental concentration range. The density of the β(Al₃Mg₂) phase along the (α(Al) + β)/β boundary was calculated and is described by a temperature-dependent polynomial.     

Densities of solid aluminum-lithium (Al-Li) alloys

Densities of solid Al and Al-Li alloys were measured by the dilatometric method for six compositions of mole fractions of lithium: 0.05,0.1,0.125,0.15,0.20, and 0.25. A curvilinear dependence of density on temperature (room temperature up to 923 K) was observed for all investigated alloys. Results could be described by parabolic equations. The molar volumes of Al-Li alloys were calculated from the density measurements. It has been found that the densities of solid Al-Li alloys initially show slightly negative deviations from linearity that reverse to positive above 0.075 mole fraction of Li. Molar volume exhibits negative deviation from linear dependence for all samples in the experimental concentration range. Power series were used to fit the dependences of density on temperature and concentration. Coefficients of volume expansion were calculated and discussed. The density of the β phase along the (α + β)/β boundary was calculated and described by a temperature-dependent polynomial.     

Activity coefficients and partial molar volumes of boron in platinum-rhodium alloys

Activity coefficients of B in the phase of Pt and of three Pt---Rh alloys with 3, 6, and 10 wt.% Rh were obtained by equilibration of B₂O₃ with H₂-H₂O mixtures between 750 and 1000 °C and subsequent determination of the B mole fraction x_B 0.06 by the mass gain of the samples or by photometric analysis. Additions of Rh to Pt have rather large but opposing effects on the partial molar enthalpies and entropies of B, resulting in partial molar excess Gibbs energies within the modest range between −40 and −55 kJ mol⁻¹. The change in the lattice contraction from −13.5 to −3.2 pm/x_B in the phase of Pt and of Pt-10Rh can be fully described in terms of a substitutional solution model with strictly constant partial molar volumes of 9.09 cm³ mol⁻¹ and 8.28 cm³ mol⁻¹ for Pt and Rh respectively and a partial molar volume for B that increases linearly from 8.2 to 8.9 cm³ mol⁻¹ between pure Pt and Pt-10Rh.     

Existence of minimum molar volumes (maximum packing densities) in morphotropic series of mixed oxides and fluorides

Plots of the cubic root of the formula volume, (V/Z)^1/3, vs. cation radius have been built for several morphotropic series of mixed oxides and fluorides. These plots are linear for isostructural compounds but exhibit discontinuities at morphotropic transitions. The classical homology rule ‘larger cation – higher its coordination number (CN) – denser the structure’ is only valid (with few exceptions) for substitutions of relatively small cations. Substitutions of large cations usually lead to opposite volume changes, regardless of increase or decrease in CNs. As a result, the densest structure types often appear with ions of somewhat intermediate size in a series. The discovery of the post-perovskite silicate phase, which greatly influenced mineralogy and geophysics, could be predicted four decades earlier, if proper attention had been paid to the small negative deviation of the layered CaIrO₃ from the plot for CaMO₃ perovskites. An analysis of the volume relations reveals some errors and leads to several predictions.     

Au-Ni合金中组元的平均原子体积和偏摩尔体积的关系

在系统合金科学框架中建立有关无序合金的平均摩尔性质（体积和势能）的函数。通过对这些函数进行推导,可以得到平均摩尔体积函数、偏摩尔体积函数及派生出与成分相关的函数。在组元的偏摩尔性质和平均摩尔性质之间的普适方程、差分方程、在偏摩尔性质和平均摩尔性质之间不同参数的约束方程和普适的Gibbs-Duhem公式。可以证明从合金平均摩尔性质的不同函数计算的偏摩尔性质是相等的,但总体来说偏摩尔性质不等于给定组元的平均摩尔性质,即偏摩尔性质不能代表相应组元的摩尔性质。通过计算Au-Ni系中组元的偏摩尔体积和平均原子体积以及合金的平均原子体积,证明所建立的公式和函数的正确性。     

Enthalpies of formation of solid Sm---Al alloys

A direct isoperibolic differential calorimeter was used to measure the formation heats of the Sm---Al intermetallic compounds. X-ray powder diffraction, optical and scanning electron microscopy and electron probe microanalysis were used to check the composition of the samples. The following values of Δ_fH⁰ for the different compounds were obtained in the solid state at 300 K: Sm₂Al, = −38.0 ± 2 kJ (mol atoms)⁻¹; SmAl, −49.0 ± 2 kJ (mol atoms)⁻¹; SmAl₂, −55.0 ± 2 kJ (mol atoms)⁻¹; SmAl₃, −48.0 ± 2 kJ (mol atoms)⁻¹. The results are discussed and compared with earlier experimental data.     

Thermodynamic investigation of the solid and liquid Au---Sb alloys

The heat content of solid and liquid AuSb₂ compound was measured from 298 K to T (375–963 K) on heating (drop method) with the help of a Tian-Calvet calorimeter. The heat capacity of the liquid compound as well as its enthalpy of fusion were deduced. The enthalpy of the liquid decreases strongly when temperature increases between the melting point and 831 K.

The enthalpy of formation of the Au---Sb melts was also determined by direct reaction calorimetry at 916 K with respect to concentration. The enthalpy of mixing is weakly negative in the whole range of concentration (_min^f = −3·47 kJ/mol at x_Au = 0·775) in agreement with the results of Béja at 923 K. disagree with the much more negative earlier data of Kameda et al. and of Hino et al. by emf and vapor pressure measurements.

Finally, the liquid/Au(cr) phase boundary determined at 916 K from the break in the h^f (x_Au) curve agrees well with the phase diagram calculated by Okamoto and Massalski but not with their experimental results.     

Investigation of solid solution hardening in molybdenum alloys

Mechanical properties of pure molybdenum like yield strength, hardness and creep strength can be modified by alloying elements. The alteration of properties can be described as a result of different mechanisms like solid solution hardening (SSH), particle as well as grain boundary hardening. The aim of this work is to quantify the solid solution hardening effect of different solutes. Therefore the influences of other strength affecting mechanisms like grain boundary hardening or particle hardening have been excluded. Based on the powder metallurgical manufacturing route different molybdenum alloys with Cr, Re, Ta, Ti or W additions were prepared. Vickers hardness measurements at room temperature and tensile tests at 500 °C were performed to quantify the hardening effect. Additionally the modulus of rigidity was measured by ultrasonic inspection and the dynamical resonance method. Lattice parameters were measured by means of X-ray diffraction experiments. Applying existing theories of solid solution hardening an attempt was made to separate and quantify dielastic and parelastic effects.     

Solid electrolyte cell studies of solid nickel-gallium alloys

Reversible galvanic cells employing ZrO₂-CaO solid electrolytes and either Pt/O₂ (air) or Ni/NiO reference electrodes were used to measure thermodynamic properties of solid Ni-Ga alloys at temperatures between 873 and 1100 K. Activities, partial Gibbs energies, and integral Gibbs energies, entropies, and enthalpies have been obtained for the a (fcc) solid solution and for the intermediate phases—Ni₃Ga, Ni₅Ga₃, Ni₃Ga₂, Ni₁₃Ga₉, NiGa, and Ni₂Ga₃. The system is characterized by negative deviations from ideality, exothermic enthalpies, and negative entropies of formation. An analysis of the latter in terms of configurational, electronic, vibrational, dilatational, and magnetic contributions is suggested.     

Solid electrolyte cell studies of solid nickel-gallium alloys

Reversible galvanic cells employing ZrO₂-CaO solid electrolytes and either Pt/O₂ (air) or Ni/NiO reference electrodes were used to measure thermodynamic properties of solid Ni-Ga alloys at temperatures between 873 and 1100 K. Activities, partial Gibbs energies, and integral Gibbs energies, entropies, and enthalpies have been obtained for the a (fcc) solid solution and for the intermediate phases—Ni₃Ga, Ni₅Ga₃, Ni₃Ga₂, Ni₁₃Ga₉, NiGa, and Ni₂Ga₃. The system is characterized by negative deviations from ideality, exothermic enthalpies, and negative entropies of formation. An analysis of the latter in terms of configurational, electronic, vibrational, dilatational, and magnetic contributions is suggested.     

Densities of molten Ni-（Cr,Co, W） superalloys

In order to obtain more accurate density for molten Ni-（Cr, Co, W） binary alloy, the densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys were measured with a sessile drop method. It is found that the measured densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys decrease with increasing temperature in the experimental temperature range. The density of alloys increases with increasing W and Co concentrations while it decreases with increasing Cr concentration in the alloy at 1 773-1 873 K. The molar volume of Ni-based alloys increases with increasing W concentration while it decreases with increasing Co concentration. The effect of Cr concentration on the molar volume of the alloy is little in the studied concentration range. The accommodation among atomic species was analyzed. The deviation of molar volume from ideal mixing shows an ideal mixing of Ni-（Cr, Co, W） binary alloys.     

Diffusion-controlled growth of solid solution scales on nickel-cobalt alloys

Cation concentration profiles in solid—solution scales on NiCo alloys have been calculated by making use of Wagner's theoretical analysis. As a result of the computation method used, it becomes unnecessary to incorporate experimental values in the calculation for either the parabolic rate constant, k_p, or the boundary conditions of the cation profile. The agreement between the independently determined theoretical and experimental cation profiles provides strong support for Wagner's model. The calculated variation of k_p with alloy composition is also in agreement with the experimental data.     

Parabolic growth of oxide solid solutions on binary alloys

The growth of oxide solid solutions on binary alloys has been described using the ternary diffusion model put forward by Wagner and subsequently modified by Dalvi and Coates and Bastow, Whittle, and Wood. A more refined defect model where the presence of all types of vacancy species within the scales is considered has been adapted to obtain the diffusivities of cations in the scales as a function of oxygen potential and cation composition. In addition, correlation effects on cation jump frequencies have been included to account for additional compositional dependence of the diffusivities. Results have been analyzed for oxidation of Ni-Co to (Ni, Co)O at 1273°K in 1 atm oxygen. Improved agreement between calculated and experimental cation concentration profiles indicates that this approach is better than to arbitrarily assign functional forms to the compositional and oxygen activity dependencies of the diffusivities, and demonstrates that an accurate as possible model for the point defect structure of the oxide is required for correct interpretation of the growth of these solid solution types of scales.Deceased July 23, 1982.     

Thermodynamic investigation of the PdPb solid alloys

With the help of a Tian-Calvet high temperature calorimeter, the enthalpy of formation of the PdPb, PdPb₂ and Pd₁₃Pb₉ compounds was determined by reaction calorimetry at room temperature. The heat content of the same intermediate compounds was measured by drop calorimetry in the solid, the liquid and the two-phase states. Their heat capacities were derived.     

Atomistic modeling of RuAl and (RuNi)Al alloys

Atomistic modeling of RuAl and RuAlNi alloys is performed. The BFS method for alloys and its first-principles-based parameters are tested by comparing to the lattice parameter and energy of formation of B2 RuAl and (Ru_50−xNi_x)Al₅₀ alloys as a function of Ni concentration. Additional tests include Monte Carlo simulations for compositions close to Ru₂₅Ni₂₅Al₅₀ showing no obvious evidence of a miscibility gap and separation of the individual B2 phases.     

Optimization of Cr/Mo molar ratio in FeCoCrMoCBY alloys for high corrosion resistance

The corrosion behavior of bulk metallic glasses (BMGs) (Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂)_100–xCr_x (x=0, 4, 8, 12, molar fraction, %) was investigated in 1 mol/L HCl aqueous solution with electrochemical tests. The electrochemical measurements demonstrate that the passive current density of Fe-based amorphous alloy is reduced by about one order of magnitude, and meanwhile, the stability of passive film can be guaranteed by the Cr/Mo molar ratio. The Mott–Schottky (M–S) curves show that the passive film is the densest when the molar ratio of Cr/Mo is between 1.37 and 1.69. X-ray photoelectron spectroscopy (XPS) analysis was performed to clarify chemical states of elements in the passive films. The results show that the corrosion resistance of the alloy is related to the molar ratio of Cr/Mo. The stability of passive film is determined by the synergistic action of Cr and Mo elements. The main component of the passive film is Cr³⁺ oxide. When the potential is greater than 0.5 V (vs SCE), Mo⁶⁺ ions play an important role in keeping the stability of the passive film. The appropriate molar ratio of Cr/Mo can reduce the dissolution rate of the passive film.