Intracrystallite liquation in ternary alloys-solid solutions

The nonequilibrium crystallization in ternary alloys—solid solutions of the A-B-C model system and actual Cu-Ni-Mn system—are calculated according to the Petrov-Scheil model. It is shown that the temperature at which the distribution coefficient of the medium-melting component is 1 and the temperature at which the content of this component in the isolated solid phase is maximal are different for intracrystallite liquation in both cases. The conditions are formulated under which the parameters of the intracrystallite liquation should be compared with the characteristics of the dendritic liquation.     

Equilibrium crystallization of alloys of ternary solid solutions

Equilibrium crystallization of continuous solid solutions in ternary systems is considered. It is shown that in each ternary and multicomponent alloy with unlimited solubility of components in the liquid and solid states, equilibrium crystallization is realized similarly to a binary alloy due to diffusion decomposition of liquid and its diffusion interaction with the previously precipitated solid phase. The distinction is the formation, at a decreased temperature, of nonequilibrium compositions of the liquid and solid phases, with conservation of the composition of the solid phase, which had been at equilibrium for the temperature before the decrease; this takes place owing to the decomposition diffusion of the liquid. The diffusion interaction of all phase components leads to the formation of equilibrium of liquid and solid phases for a new temperature. By plotting and calculation, it is shown that in ternary systems, for certain alloy compositions at definite stages of crystallization, the fraction of the solid phase can decrease due to the diffusion interaction, which is excluded for solid solutions of binary alloys.     

Phase equilibria in the titanium corner of hypoeutectic alloys in the Ti-Nb-Si-Al system

Physicochemical analysis methods have been applied to the phase equilibria in the Ti-Nb-Si-Al system in the region of alloys rich in titanium. It is found that the crystallization conditions for hypoeutectic alloys with constant 5 at.% aluminum content control the niobium contents up to 17.5 at.%, for which there are two groups. After the primary crystallization of the β phase in alloys in these groups, binary eutectics are formed with different intermetallic phases. The properties of the alloys are dependent on the phase compositions in the eutectic mixtures. The temperature and concentration stability of the phases have been determined. It is shown that a peritectic reaction may give rise to a second intermetallide phase in alloys approximating to equilibrium as a result of subsequent annealing, which does not affect the structure of the cast alloys.     

Three Component raoultian behavior in relation to metal refining by crystallization and reflux

A form of ternary solution behavior is derived, and used to predict the movement of elements between solid and liquid phases during metal refining by crystallization and reflux. This behavior is termed “Raoultian ternary behavior” because it refers to composition regions in which the solvent metal predominates,i.e. the impurities are present at dilute concentrations. Raoultian ternary solution behavior is limited to the solvent side of eutectic systems, for sufficiently high solvent concentrations; it is independent of the behavior of the system in the hypereutectic regions. It is shown, firstly, that the extent of solid solubility of an impurity in a dilute binary system may be predicted from latent heat of fusion and melting point data and the location of the liquidus line and, secondly, that by combining such data for two impurity-solvent binary systems it is possible to calculate the behavior of the corresponding dilute ternary system. It is also shown that Raoultian ternary behavior requires that the solidus and liquidus curves, on an isothermal composition diagram, be straight lines. The application of Raoultian solution behavior is discussed in relation to the prediction of the number of theoretical steps obtained during the operation of a crystallization and reflux column, and the practical results obtained.     

Alloys and phase equilibria in the Al-Ti-Rh system. II. Melting diagram of the TiRh-Rh-AlRh partial system

Data on the solidus surface of the partial TiRh-Rh-AlRh system and results of metallography, x-ray diffraction, and differential thermal and electron microprobe analyses of its as-cast alloys are used to project the liquidus surface of this system onto the concentration triangle and examine the processes occurring in the crystallization of its alloys for the first time. This makes it possible to plot the melting diagram of the partial TiRh-Rh-AlRh system. Its liquidus surface is completed with four surfaces of primary crystallization of solid solutions based on rhodium and phases based on binary compounds formed in the bounding binary Al-Rh and Ti-Rh systems. In the partial TiRh-Rh-AlRh system, there are two invariant four-phase equilibria involving liquid; one of them is peritectic (at 1714°C) and the other is eutectic (at 1675°C). These four-phase equilibria also include five monovariant three-phase equilibria involving a liquid phase.     

Search for metallic glasses at eutectic compositions in the Ag-Cu-Ge,Ag-Cu-Sb and Ag-Cu-Sb-Ge systems

Phase relationships have been examined in several slowly cooled ternary Ag-Cu-Ge, Ag-Cu-Sb, and quaternary Ag-Cu-Ge-Sb alloys, by means of optical and electron metallography, including electron microprobe. The obtained results have been used to locate the compositions of eutectic points, and also to establish the related details of the surfaces of primary crystallization. The composition regions likely to yield metallic glasses were explored by rapid melt quenching using the spinning wheel technique. Amorphous ribbons were obtained from alloys in the region of the lowest melting eutectic in the Ag-Cu-Ge system, but not in the Ag-Cu-Sb and Ag-Cu-Ge-Sb systems. However, metallic glass was produced in two Ag-Cu-Sb alloys with compositions along a pseudobinary eutectic line at an electron concentration ofe/a = 1.8. This is the same value as that associated with metallic glass formation at the ternary eutectic composition in the Ag-Cu-Ge system. All obtained metallic glasses were found to have relatively low crystallization temperatures in the range between 140 and 170 °C.     

Study on the estimation of the hydrogen diffusivity in liquid Fe-base ternary system containing substitutional alloying elements

The first-order approximated quasi-chemical model of Fe-base ternary system containing interstitial and substitutional solutes suggested by R. B. McLellan have been modified for dilute solid solutions with assumption that the interaction energy (?_ii) between interstitial solutes is zero. The interaction energy (Δ ?) between substitutional and interstitial atom and the diffusivities of interstitial elements in various substitutional compositions of Fe base system are calculated using published solubility of the system and diffusivity of Fe-interstitial binary data with above model. The hydrogen diffusivities in liquid Fe base binary alloys predicted by the above model with the assumption of ?_HH = 0 agree well with experimental results.     

Solidification of a binary eutectic in a three-component system

The change in mass and composition of the phases during the equilibrium solidification of eutectic alloys in three-component systems is considered. For the model system A-B-C, we show that equilibrium solidification of binary eutectics in three-component systems is determined by processes of decomposition and interaction, as in the crystallization of a solid solution. Eutectic transformation is generally associated with equilibrium solidification, since decomposition dominates over interaction. These findings are confirmed by studying solidification in the Al-Si-Cu system.     

Prediction of Activities in Fe-Based Ternary Liquid Alloys by Hoch-Arpshofen Model

 Thermodynamic properties for an alloy system play an important role in the materials science and engineering. Therefore, theoretical calculations having the flexibility to deal with complexity are very useful and have scientific meaning. The Hoch-Arpshofen model was deduced from physical principles and is applicable to binary, ternary and larger system using its binary interaction parameters only. Calculations of the activities of Fe-based liquid alloys are calculated using Hoch-Arpshofen model from data on the binary subsystems. Results for the activities for Fe-Au-Ni, Fe-Cr-Ni, Fe-Co-Cr and Fe-Co-Ni systems at required temperature are presented by Hoch-Arpshofen model. The average relative errors of prediction are 78%, 45%, 49% and 27%, respectively. It shows that the calculated results are in good agreement with the experimental data except Fe-Au-Ni system, which exhibits strong interaction between unlike atoms. The model provides a simple, reliable and general method for calculating the activities for Fe-based liquid alloys.     

Warm-temperature tensile ductility in Al-Mg alloys

Several binary and ternary Al alloys containing from 2.8 to 5.5 wt pct Mg were tested in tension at elevated temperatures (200 °C to 500 °C) over a range of strain rates (10⁻⁴ to 2.0 s⁻¹). Tensile ductilies of up to 325 pct were obtained in binary Al-Mg alloys with coarse grains deformed in the solute-drag creep regime. Under test conditions in which solute-drag creep controls deformation, Mg in concentrations from 2.8 to 5.5 wt pct neither affects tensile ductility nor influences strain-rate sensitivity or flow stress significantly. Strength is shown to increase with increasing Mg concentration, however, in the power-law-breakdown regime. The solute-drag creep process, which leads to superplastic-like elongations, is shown to have no observable grain-size dependence in a binary Al-Mg material. Ternary alloying additions of Mn and Zr are shown to decrease the strain-rate sensitivity during solute-drag creep, negatively influencing ductility. An important cause of reduced ductility in the ternary alloys during creep deformation is found to be a transition from necking-controlled failure in the binary alloys to cavitation-controlled failure in the ternary alloys investigated. An increase in ternary element concentration, which can increase the relative volume percentage of proeutectic products, increases cavitation.     

Warm-temperature tensile ductility in Al−Mg alloys

Several binary and ternary Al alloys containing from 2.8 to 5.5 wt pct Mg were tested in tension at elevated temperatures (200°C to 500°C) over a range of strain rates (10⁻⁴ to 2.0 s⁻¹). Tensile ductilities of up to 325 pct were obtained in binary Al−Mg alloys with coarse grains deformed in the solute-drag creep regime. Under test conditions in which solute-drag creep controls deformation, Mg in concentrations from 2.8 to 5.5 wt pct neither affects tensile ductility nor influences strain-rate sensitivity or flow stress significantly. Strength is shown to increase with increasing Mg concentration, however, in the power-law-break down regime. The solute-drag creep process, which leads to superplastic-like elongations, is shown to have no observable grain-size dependence in a binary Al−Mg material. Ternary alloying additions of Mn and Zr are shown to decrease the strain-rate sensitivity during solute-drag creep, negatively influencing ductility. An important cause of reduced ductility in the ternary alloys during creep deformation is found to be a transition from necking-controlled failure in the binary alloys to cavitation-controlled failure in the ternary alloys investigated. An increase in ternary element concentration, which can increase the relative volume percentage of proeutectic products, increases cavitation.     

Thermochemical Properties of Liquid Alloys in Fe ― O and Fe ― O ― Metal Systems

An isoperibolic calorimeter has been used to determine the partial and integral enthalpies of mixing for liquid alloys in the binary Fe ― O system and ternary Fe ― O ― M ones at 1915 K. The enthalpies of mixing in these systems are high exothermic quantities, which agree with published data. It is found that the first partial enthalpy of mixing for oxygen is _280 kJ/mole. The enthalpies of mixing have been calculated from the standard enthalpies of formation Δ_f H ^º ₂₉₈ for iron oxides throughout the concentration range. The enthalpies of mixing have been calculated and measured for binary alloys in the Fe ― O system, which are correlated one with the other.     

Thermodynamic calculations of the effective solidification range and its relation to hot cracking of aluminum-based ternary alloys

The correlation between experimental hot cracking (HC) and the calculated effective solidification range (ESR) (obtained as the difference between the formation temperature of a definite amount (65–90 wt %) of the solid phase and the nonequilibrium solidus temperature) is investigated by the example of Al-Cu, Al-Mg, and Al-Si binary systems. It is revealed that the location of the HB peak almost coincides with the calculated ESR peak. A good convergence between the calculated and experimental ESRs is established. The correlation between the HB and calculated ESR is, in general, considerably worse in the studied Al-Cu-Mg, Al-Cu-Si, and Al-Si-Mg ternary systems. It is shown that a correlation between the HB and calculated ESR that is similar to binary systems can be obtained for the radial joins of ternary systems if all alloys compared by the HB are crystallized by identical reactions with the participation of identical phases.     

Influence of iron and silicon on the phase composition and structure of heat-resistant casting nikalines strengthened by nanoparticles

The phase composition of the Al-Ni-Mn-Fe-Si-Zr system is analyzed as applied to heat-resistant nikalines (aluminum alloys of a new generation based on Ni-containing eutectic), which are strengthened by the Al₃Zr (L1₂) nanoparticles. It is shown that the presence of iron and silicon considerably complicates the phase analysis when compared with the AN4Mts2 base alloy. Silicon strongly widens the crystallization range, which increases the tendency of the alloy to form hot cracks during casting. It is shown that economically doped nikaline AN2ZhMts substantially exceeds the most heat-resistant cast aluminum alloys of the AM5 grade in the totality of its main characteristics (heat resistance and mechanical and production properties).     

M-Si-B合金非晶形成能力的CALPHAD模式评估

Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach@長谷部光弘$日本九州工业大学 @OHTANI Hiroshi$Department of Materials Science and Engineering, Kyushu Institute of Technology @HASEBE Mitsuhiro$Department of Materials Science and Engineering, Kyushu Institute of Technology…     

Sulfidation under atmospheric conditions of Cu-Ni,Cu-Sn,and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems

The corrosion susceptibility of binary and ternary alloys can be assessed by controlled exposures to corrosive environments of samples selected from different regions of the phase diagram. To conduct such studies, we have prepared 24 high purity alloys from the Cu-Ni, Cu-Sn, and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems. Samples of these alloys were then exposed for varying periods to atmospherically realistic concentrations of hydrogen sulfide in humidified air. The resulting sulfurization of the samples is presented in a series of chromatic plots developed as part of this research. The ability of binary alloying metals to retard the sulfidation of copper follows the order Zn > Ni > Sn. The Cu-Ni-Zn ternary alloys are more resistant to sulfidation than Cu-Ni-Sn alloys for the same extent of solid solution alloying; in fact, alloys in the Cu-Ni-Zn system with ≤70 pct copper proved to be extremely resistant to sulfidation. In both ternary systems, the relative performance of the alloys was different at different exposure periods, a result that emphasizes the importance of monitoring corrosion throughout realistic exposures if the results are to be used in the selection of materials for field applications.     

Sulfidation under atmospheric conditions of Cu-Ni,Cu-Sn,and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems

The corrosion susceptibility of binary and ternary alloys can be assessed by controlled exposures to corrosive environments of samples selected from different regions of the phase diagram. To conduct such studies, we have prepared 24 high purity alloys from the Cu-Ni, Cu-Sn, and Cu-Zn binary and Cu-Ni-Sn and Cu-Ni-Zn ternary systems. Samples of these alloys were then exposed for varying periods to atmospherically realistic concentrations of hydrogen sulfide in humidified air. The resulting sulfurization of the samples is presented in a series of chromatic plots developed as part of this research. The ability of binary alloying metals to retard the sulfidation of copper follows the order Zn > Ni > Sn. The Cu-Ni-Zn ternary alloys are more resistant to sulfidation than Cu-Ni-Sn alloys for the same extent of solid solution alloying; in fact, alloys in the Cu-Ni-Zn system with ≤70 pct copper proved to be extremely resistant to sulfidation. In both ternary systems, the relative performance of the alloys was different at different exposure periods, a result that emphasizes the importance of monitoring corrosion throughout realistic exposures if the results are to be used in the selection of materials for field applications.     

Modeling solid solution strengthening in nickel alloys

The yield stress of multicomponent nickel solid solution alloys has not been modeled in the past with respect to the effects of composition and temperature. There have been investigations of the effect on the yield stress of solutes in binary systems at a fixed temperature, but the effects on the yield stress of multiple solute elements and temperature changes have not been investigated. In this article, two different forms of the trough model are considered for nickel-base alloys to determine the most applicable model for solid solution strengthening in the system. The yield stresses of three binary nickel-chromium and three ternary nickel alloys were determined at a range of temperatures. The yield stress of the alloys was then modeled using the Feltham equation. The constants determined in fitting the Feltham equation to the experimental data were then applied to other experimental solid solution alloys and also to published information on commercial solid solution nickel alloys. It was found that the yield stress of the nickel solid solution alloys could be modeled successfully using the Feltham equation.     

Phase stability and phase transformations in plutonium and plutonium-gallium alloys

The complexity of phase stability and transformations in plutonium alloys is reflected in the plutonium-gallium (Pu-Ga) phase diagram, which is perhaps the most complex of all binary systems. Although many investigations have explored phase equilibria, transformation systematics, and structure/property relations in the Pu-Ga system, many outstanding problems remain and new issues regularly appear. In this article, we describe recent dilatometry and calorimetry measurements on pure plutonium and plutonium-gallium alloys. We also present recent phase diagram modeling that attempts to unravel differences between the U.S. and Russian Pu-Ga phase diagrams. The ultimate goal of this work is to produce the first internally consistent database of thermophysical properties of this system so that a true equilibrium phase diagram can be produced and so that stability can be predicted over a range of conditions. This article is based on a presentation in the symposium “Terence E. Mitchell Symposium on the Magic of Materials: Structures and Properties” from the TMS Annual Meeting in San Diego, CA in March 2003.