Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

金银合金真空分离的理论研究（英文）

为准确预测金银合金真空蒸馏过程中产品成分与温度和压力的关系,并为工业生产参数的设计提供便捷和有效的指导,根据分子相互作用体积模型(MIVM),计算不同温度下金银合金的分离系数(β)和气-液平衡成分。结合气液相平衡(VLE)理论,绘制金银合金真空蒸馏的温度-成分、压力-成分相图。同时,对金、银三相点和金、银蒸气冷凝温度进行计算。理论研究结果表明：随着蒸馏温度的升高,分离系数减小,金在气相中的含量增加;低温对分离金银具有积极效果;在压强1～10 Pa范围内,金、银冷凝温度相差约450 K。     

Modeling steel corrosion under supercritical CO2 conditions

Corrosion in the presence of CO₂ was studied under supercritical conditions (high pressure and moderate temperature) using different carbon steels and various corrosion resistant alloys (CRA's). An objective of this work was, among others, to put the results in perspective relative to various CO₂ corrosion models that have been developed and published over the years. In particular, the NORSOK, FREECORP, and OLI models were used for comparison, while others were discussed as well. The systems investigated were (a) supercritical CO₂ (SC CO₂) saturated with water (no separate water phase), (b) a water mist phase in equilibrium with SC CO₂, (c) a water/brine phase in equilibrium with SC CO₂. It was found that the OLI model best simulates the experimental corrosion rates observed in system (c) where coupons were corroded in the aqueous phase at high velocities in the rotating cage. The varying susceptibility of different carbon steels to corrosion under these conditions is highlighted. CRA steels are comparatively more resistant.     

应用本构模型和神经网络模型预测铝/镁基纳米复合材料的高温流变行为(英文)

为了预测Al/Mg基纳米复合材料的高温流变行为,在不同的应变速率(0.01-1.0s-)和温度(523,623和1723K)的条件下进行热压缩试验,利用所得到的应力-应变数据,开发了本构模型,比如一般流动方程。阿累尼乌斯双曲模型、Johnson-Cook(JC)和改性的Zerilli-Armstrong(ZA)模型及人工神经网络(ANN)模型。通过使用统计参数,例如均方根误差(RMSE)、回归系数(R2)、平均相对误差(MRE)和分散指数(Is),比较了人工神经网络和不同的本构模型。结果表明,人工神经网络模型对AA5083-2%TiC复合材料的热变形流动应力的评估准确性更高。     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3, CrO-Cr2O3-Al2O3, and CrO-Cr2O3-CaO systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃, CrO-Cr₂O₂-Al₂O₃, and CrO-Cr₂O₂-CaO systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air in the case of the first two systems and toP _{O 2} = 10^?3 atm for the CrO-Cr₂O₃-CaO system. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Prediction of the global volatilization rate of gas-metal-alloy reaction systems—Method of calculation

The methods and equations used to predict the global volatilization rate of high temperature gas-solid reactions have been presented. The procedure includes the formulation of Bartlett's model, determining the equilibrium constant, and the estimation of the nonequilibrium properties of gases at high temperatures. For the alloy system forming the protective Cr₂O₃ layer, the global volatilization rate can be estimated with a modified Tedmon's model using a nonlinear regression technique.Prepared for the U.S. Department of Energy under contract No. W-7405-ENG-82.     

Correlation and prediction of interface tension for fluid mixtures: An approach based on cubic equations of state with the wong-sandler mixing rule

Concentration profiles, interface thickness, and interface tensions have been calculated for mixtures applying the gradient theory to the Peng-Robinson equation of state. The approach is based on an accurate local fit of vapor-liquid equilibrium (VLE) data, and, for this purpose, the flexibility of the original Wong-Sandler mixing rule has been taken into account. Correlation and prediction capabilities of experimental interfacial tension data are analyzed for the quadratic mixing rule and the present approach. The method, which is discussed in detail in this work, provides an improved scheme for calculating interfacial properties, both for polar and nonpolar mixtures. According to results, a better correlation and prediction of the interfacial tensions can be obtained from an adequate interpolation of the VLE, using simple cubic equations of state. Examples are presented for binary and ternary mixtures.     

Prediction of effect of volume fraction, compact pressure and milling time on properties of Al-Al2O3 MMCs using neural networks

An artificial neural network (ANN) model was developed to predict the effect of volume fraction, compact pressure and milling time on green density, sintered density and hardness of Al-Al₂O₃ metal matrix composites (MMCs). Al-Al₂O₃ powder mixtures with various reinforcement volume fractions of 5, 10, 15% Al₂O₃ and milling times (0 h to 7 h) were prepared by mechanical milling process and composite powders were compacted at various pressure (300, 500 and 700 MPa). The three input parameters in the proposed ANN were the volume fraction, compact pressure and duration of the milling process. Green density, sintered density and hardness of the composites were the outputs obtained from the proposed ANN. As a result of this study the ANN was found to be successful for predicting the green density, sintered density and hardness of Al-Al₂O₃ MMCs. The mean absolute percentage error for the predicted values didn’t exceed 5.53%. This model can be used for predicting Al-Al₂O₃ MMCs properties produced with different reinforcement volume fractions, compact pressures and milling times.     

Phase Equilibria in the System FeO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

Liquidus data are presented for mixtures in the ternary system FeO-Fe₂O₃-SiO₂ in equilibrium with a gas phase with O₂ pressures ranging from 10^?10.9 to 1 atm. Data obtained are combined with previously published data to construct lines of equal O₂ pressures and lines of equal CO₂/H₂ mixing ratios along the liquidus surface. Courses of crystallization of selected mixtures under conditions of constant total composition, constant O₂ pressures, and constant CO₂/H₂ mixing ratios are discussed.     

Corrosion investigation of J55 steel under simulated enhanced oil recovery conditions using CO2 flooding

The present work investigated corrosion behaviour of J55 tubing steels and solution equilibrium chemistry of the produced water under simulated CO₂ flooding environments at various temperatures. The corrosion rates were calculated by weight loss method carried out with or without one kind of imidazoline based inhibitor in autoclave. Surface morphologies of corrosion product films formed on samples were analysed using scanning electron microscopy (SEM). Meanwhile, the concentrations of main solution species in experimental produced water were tested. The solution equilibrium chemistry of dissolved CO₂ in the produced water was also calculated and analysed. The results indicated that corrosion rate of J55 significantly increased when temperature exceeded 55°C and greatly decreased with the effect of inhibitor especially when the imidazoline based inhibitor exceeds 150 ppm, σ Fe concentration increased with the increase in temperature, especially when temperature exceeded 44°C. The H₂CO₃ concentration declines by about 3 orders of magnitude compared to CO₂(aq) concentration and the yielded HCO₃^? concentration is about 0·2–0·35 times of the H₂CO₃ concentration.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3, CrO-Cr2O3-Al2O3, and CrO-Cr2O3-CaO systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃, CrO-Cr₂O₂-Al₂O₃, and CrO-Cr₂O₂-CaO systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air in the case of the first two systems and toP _{O 2} = 10⁻³ atm for the CrO-Cr₂O₃-CaO system. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Corrosion-resistant alloy testing and selection for oil and gas production

ABSTRACT

Corrosion-resistant alloys (CRAs) are employed in severe oil and gas production environments that operate at high pressures and temperatures and contain chlorides, CO₂, and H₂S. They exhibit high resistance to uniform corrosion in these environments due to their passivity. However, they can suffer from different forms of environmentally assisted cracking (EAC), depending on the environmental and metallurgical conditions. This paper reviews the recent literature of EAC in CRAs and presents an overall framework for evaluating the SCC based on electrochemical modelling of corrosion and repassivation potentials for localised corrosion. The modelling is supported by experimental data on crack growth as a function of environmental variables, alloy content, and potential.

This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17).     

Equilibrium phase relationships in the system Cu-O under high oxygen pressure

The equilibrium phase relationships near the liquidus line of the system Cu₂O-CuO-O₂ (a part of wider system Cu-O) were determined under pure oxygen pressure from 0.001 to 11 MPa by three experimental methods: differential thermal analysis (DTA), thermogravimetry (TG), and thermobarometry (TB). The coordinates of the eutectic point between solid Cu₂O and CuO were found to be P _{O 2}=0.069±0.001 MPa and T=1364±1 K. It was proved experimentally that, at least at temperatures up to 1526 K and oxygen pressures up to 11 MPa, CuO melts incongruently with liberation of gaseous oxygen and with the temperature dependence of P _{O 2} obeying an Arrheniustype equation. The conditions for congruent melting of CuO were analyzed using the model, and it was found that congruent melting of CuO should occur at ≈ 1620 K under oxygen pressure ∼1000 MPa.     

Equilibrium phase relationships in the system Cu-O under high oxygen pressure

The equilibrium phase relationships near the liquidus line of the system Cu₂O-CuO-O₂ (a part of wider system Cu-O) were determined under pure oxygen pressure from 0.001 to 11 MPa by three experimental methods: differential thermal analysis (DTA), thermogravimetry (TG), and thermobarometry (TB). The coordinates of the eutectic point between solid Cu₂O and CuO were found to be P _{O 2}=0.069±0.001 MPa and T=1364±1 K. It was proved experimentally that, at least at temperatures up to 1526 K and oxygen pressures up to 11 MPa, CuO melts incongruently with liberation of gaseous oxygen and with the temperature dependence of P _{O 2} obeying an Arrheniustype equation. The conditions for congruent melting of CuO were analyzed using the model, and it was found that congruent melting of CuO should occur at ≈ 1620 K under oxygen pressure ∼1000 MPa.     

Determination of liquid-phase boundaries in Zn-Fe-Mx systems

Iron solubilities in molten Zn-Al alloys were experimentally determined at temperatures from 450 to 480 °C, a range relevant to continuous galvanizing operation. The Fe solubility was found to decrease slowly with increasing Al content in regions where ζ (FeZn₁₃) or δ (FeZn₇) is the equilibrium compound and rapidly in the region where the η (Fe₂Al₅Zn _x ) phase is the equilibrium compound. Analyses of the experimental data indicated that Fe solubility is governed by the thermodynamic properties of the intermetallic compound in equilibrium with the molten Zn-Al alloy. A model was developed to describe the liquid surface in the Zn-rich corner of the Zn-Fe-Al system. The methodology developed in the exercise has proven applicable for the determination of the liquid surface in the Zn-Fe-Ni system.     

Determination of liquid-phase boundaries in Zn-Fe-Mx systems

Iron solubilities in molten Zn-Al alloys were experimentally determined at temperatures from 450 to 480 °C, a range relevant to continuous galvanizing operation. The Fe solubility was found to decrease slowly with increasing Al content in regions where ζ (FeZn₁₃) or δ (FeZn₇) is the equilibrium compound and rapidly in the region where the η (Fe₂Al₅Zn _x ) phase is the equilibrium compound. Analyses of the experimental data indicated that Fe solubility is governed by the thermodynamic properties of the intermetallic compound in equilibrium with the molten Zn-Al alloy. A model was developed to describe the liquid surface in the Zn-rich corner of the Zn-Fe-Al system. The methodology developed in the exercise has proven applicable for the determination of the liquid surface in the Zn-Fe-Ni system.     

Experimental Investigation of Gas/Matte/Spinel Equilibria in the Cu-Fe-O-S System at 1473 K (1200 °C) and <Emphasis Type="Italic">P</Emphasis>(SO<Subscript>2</Subscript>) = 0.25 atm

The Cu-Fe-O-S system is the key system for the characterisation of the phase chemistry in high-temperature copper making processes. An experimental study was undertaken to investigate the gas/matte/spinel equilibria in the Cu-Fe-O-S system at 1473 K (1200 °C), P(SO₂) = 0.25 atm, and a range of oxygen partial pressures. The experimental methodology involved high temperature equilibration using a primary phase substrate technique in controlled gas atmospheres (CO/CO₂/SO₂/Ar), rapid quenching of the equilibrated phases, followed by direct measurement of phase compositions using electron probe x-ray microanalysis. Particular attention was given to the analysis of reactions during equilibration and confirmation of the achievement of equilibrium in the present study. The new data provide important information for understanding of the gas/matte/spinel interactions at high temperature and provide an essential foundation for the development of the multicomponent thermodynamic database for copper-containing systems.     

The Nickel-Rich Region of the Ni-Ge Phase Diagram

We present new results on the phase boundaries separating the single and the 2-phase regions of the Ni-rich Ni-Ge phase diagram. The accuracy of the boundary between the 2-phase Ni(Ge) + Ni₃Ge and single-phase Ni₃Ge region is reinforced by the addition of new data obtained from dissolution experiments. This boundary is consistent with the results of a recent thermodynamic model at temperatures lower than ~840 °C, but is leaner in Ge content at higher temperatures. Additional data on the equilibrium solubility of Ge in Ni (Ni₃Ge solvus) reinforces the accuracy of the phase boundary to temperatures as low as 700 °C; these data are not new, but are not included in the most recent assessments. The recent thermodynamic model of the Ni₃Ge solvus is in remarkably good agreement with the experimental results. The composition dependence of the ferromagnetic Curie temperature, T _c, is also re-evaluated by the addition of data not previously included in recent assessments. The dependency of T _c on Ge content is essentially linear to concentrations of ~13% Ge, which exceeds the solubility of Ge in Ni-Ge alloys. Empirical equations relating equilibrium compositions and temperatures of the phase boundaries and the composition dependence of T _c are presented.     

Compositional optimization of glass forming alloys based on critical dimension by using artificial neural network

An artificial neural network (ANN) model was developed for simulating and predicting critical dimension d_c of glass forming alloys. A group of Zr-Al-Ni-Cu and Cu-Zr-Ti-Ni bulk metallic glasses were designed based on the d_c and their d_c values were predicted by the ANN model. Zr-Al-Ni-Cu and Cu-Zr-Ti-Ni bulk metallic glasses were prepared by injecting into copper mold. The amorphous structures and the determination of the d_c of as-cast alloys were ascertained using X-ray diffraction. The results show that the predicted d_c values of glass forming alloys are in agreement with the corresponding experimental values. Thus the developed ANN model is reliable and adequate for designing the composition and predicting the d_c of glass forming alloy.