bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple Solution Approaches in Phase Diagram Evaluation
Authors: Kaufman Larry 
Published: March 2011

ABSTRACTIn the beginning there were ideal solutions (Geneva 1966) [1] and lattice stability values were deduced for the transition elements. Next regular solution interaction parameters for second and third row transition elements were predicted from simple models (Cambridge 1970)[2] combined with the lattice stability values via computer methods to calculate binary and ternary phase diagrams. Line compounds were introduced for comparison with experimental phase diagram data. At Brunel (1971)[3] and Munster (1972)[4] the regular solution models were expanded to include subregular and higher order terms and since the origin of CALPHAD (1973)[5]many coupled sets of thermochemical and phase diagram descriptions have been derived and published. Examples of multicomponent phase diagram calculations applied to solution of industrial problems have been illustrated in the subject areas of transformations and stability in steels and superalloys, uranium alloys, SIALON materials, metallic and fluoride glasses, electronic materials, and novel materials refining and processing methods. [6-19]
The Sublattice Model
Authors: Sundman BO , Ågren John 
Published: March 2011

ABSTRACTA thermodynamic model, based on the regular solution approximation is presented and a formalism, suitable for phases with an arbitrary number of elements and sublattices is described. A new concept, the component array, is introduced in order to simplify the analytical expressions for the Gibbs energy. The mathematical complexity of the model has been solved by the implementation of the model as a part of a general software system for thermochemical and phase diagram calculations by computer.The sublattice model is suitable for describing phases where the difference in size, charge or electronegativity causes a deviation from random mixing of the atoms in a manner which can be described as long range order. This is the case for interstitial solutions and many intermetallic phases, but also for ionic liquids and slag systems. The application of the model to several alloy system will be described.
A Pair-Wise Interaction Model for Multi-Sublattice Phases
Authors: Pratt J.N. , Jones I.P. 
Published: March 2011

ABSTRACTThe use of simple nearest neighbour pair-wise interaction models for the description of the thermodynamic properties of ordered alloys is reviewed and extended to the treatment of phases containing several sublattices. Employing individual sublattice occupation parameters to define atomic distributions, enthalpies corresponding to these are described by the summation of pair-wise interaction energies over all the resulting first co-ordination shell neighbours. Invariant like and unlike bond energies are assumed, their respective values being estimated using heats of vaporisation of the elements and a heat of formation of the phase at a single composition. Combination of the enthalpies with corresponding configurational entropies yields an expression for the free energy of the phase which may be minimised with respect to variation of the sublattice occupation parameters. This leads to the prediction of the stable atomic distributions and the variation of these and the thermodynamic properties with composition. The application of the model to sigma phases and other multi-sublattice structures is discussed
Association Model for Liquid Alloys
Authors: Sommer Ferdinand 
Published: March 2011

ABSTRACTThe concentration and the temperature dependence of thermodynamic mixing functions of liquid alloys with compound formation tendency, which often exhibit large deviations from a regular behavior, can be calculated according to an association model using only a few parameters which have a definite physical significance. The results obtained for binary and ternary alloy melts with one ore more, simultaneously occurring, binary or ternary associates are in good accordance with the experimental values. For the calculation of phase diagrams, the association model enables a correct extrapolation into concentration and temperature regions for which no experimental results are available. The occurrence and the borderline of miscibility gaps in liquid alloys with strong compound forming tendency can be quantitatively described.
Cohesion, Compound Formation and Phase Diagrams from First Principles
Authors: Williams A. R. , Gelatt C. D. , Connolly J. W. D. , Moruzzi V. L. 
Published: March 2011

ABSTRACTThe physical picture of cohesion and compound formation provided by parameter-free, self-consistent, energy-band calculations will be described. For transition-metal elements, the calculations allow us to “see” which electrons are holding the solid together and which are holding it apart. For compounds, calculated heats of formation agree well with available measurements and are in general agreement with those given by Miedema's empirical formula. (The agreement with Miedema is paradoxical, in that Miedema's conception of the formation process differs qualitatively from ours.) Preliminary, but very encouraging, results of efforts to extend the analysis to disordered materials and to the calculation of phase diagrams are described.
Magnetic Ordering and Phase Separation in Binary Alloys with One Magnetic Component
Authors: Moran-Lopez J.L. , Urias Jesus 
Published: March 2011

ABSTRACTMagnetic ordering and phase separation in binary alloys with one magnetic component are studied within the mean field approximation. The influence of ferromagnetic ordering on the phase separation temperature (TCS) is examined in detail. In general it is found that magnetism increases TCS and causes strong asymmetries in the phase diagram. In particular, it is found that in systems with only ferromagnetic interactions, the Curie temperature (TCM) and TCS are the same. Results for the phase diagrams and for the temperature dependence of the magnetic and spatial order parameters are presented.
Phase Diagram Features Associated with Multicritical Points in Alloy Systems
Authors: Allen Samuel M. , Cahn John W. 
Published: March 2011

ABSTRACTMany features in the vicinity of critical points in phase diagrams can be illustrated using a Landau type free energy expansion as a power series in one or more order parameters and composition. This simple approach can be used with any solution model. It also predicts limits to metastability, and is useful for understanding mechanisms of phase change. The theory is applied to all the critical points that can occur in binary systems according to a Landau theory: critical consolute points, order-disorder transitions, tricritical points, critical end points, as well as to systems in which two transitions such as chemical and magnetic ordering occur.
A Thermodynamic Approach to the Calculation of the C-Cr-Nb-Ni-W Phase Diagram
Authors: Chevalier P.Y. , Barbier J.N. , Ansara I. 
Published: March 2011

ABSTRACTThe phase boundaries of the C-Cr-Nb-Ni-W system are calculated from the available thermodynamic properties of the limiting binary systems. The methods of calculation and the models used in the description of the ternary and quaternary systems are presented as well as the influence of tungsten on the solubility of the M23C6phase in the nickel rich alloys.
Prediction of Solid + Liquid Equilibrium Diagrams for Binary Mixtures Forming Solid Solutions with an Extremum
Authors: Brostow Witold , Antonieta Macip M. 
Published: March 2011

ABSTRACTConvenient methods of correlation and prediction of S+L diagrams exist only for systems forming eutectics. To deal with solid solutions, we have adopted the model of strictly regular solutions of Guggenheim [3–5]. Our key assumption is that values of the Gibbs function of interchange w are different in the two coexisting phases: wS and wL. The assumption is based on the fact that the average interatomic distances R are also different, and this affects the averages of the interatomic (or intermolecular) potentials. The input parameters are enthalpies and temperatures of melting of pure components and any pair of experimental points on the diagram. For a number of binary alloy systems the agreement with the experiment is good. Since we believe in the basic unity of materials (see Chap. 1 in [7]), calcuations have also been made for organic mixtures, again with good results.
Use of Metastable Phase Diagrams in Rapid Solidification
Authors: Perepezko J. H. , Boettinger W. J. 
Published: March 2011

ABSTRACTDuring rapid solidification, the nucleation and/or growth of a thermodynamically stable phase may be difficult. In this case the liquidus, solidus or other thermodynamic data for a metastable phase are important for the interpretation and prediction of the phases present in rapidly solidified materials. In this paper various techniques are described to obtain information about metastable equilibrium from measured stable equilibrium data. Extrapolations of phase boundaries as functions of temperature, pressure or composition (including a new component) into regions of metastability can often be constructed directly on the equilibrium diagram. These constructions can be performed more quantitatively with analytical methods using thermodynamic modelling of the free energy functions consistent with measured data. A number of examples are considered including a discussion of metastable liquid miscibility gaps, metastable eutectic and peritectic reactions, pressure diagrams and metastability in ternary alloys to indicate the possible product phase selection. A coupling of metastable phase diagrams with a solidification kinetics analysis can contribute towards effective alloy design and processing during rapid solidification.
Theory of Surface Effects in Binary Alloys
Authors: MoráN-LóPez J.L. , Falicov L.M. 
Published: March 2011

ABSTRACTThe chemical, ordering and magnetic properties of binary alloys at the surface are examined in terms of a model of pairwise interacting atoms. Both the case of segregating alloys and the case of alloys which form intermetallic compounds are examined. Some surprising results about surface concentration and surface ordering are found. Applications to a number of systems, including ferromagnets, are presented.
Paraequilibrium and other Restricted Equilibria
Authors: Hillert Mats 
Published: March 2011

ABSTRACTAfter a review of the historic development of the concept of paraequilibrium in the field of alloyed steels, the basic principles of restricted thermodynamic equilibrium at a migrating interface during phase transformations are outlined. As a demonstration they are first applied to classical nucleation. In addition to the case of paraequilibrium they are then applied to adiabatic and to isochoric conditions. It is argued that a full equilibrium model, with a spike of the intensive property in front of the migrating interface may be more realistic. It is shown that the full equilibrium conditions require about twice as much undercooling or underpressure as the restricted equilibrium conditions because of the consumption of driving force in the spike.
The concept of restricted equilibrium only applies to heterogeneous phase transformations. For homogeneous reactions, the same experimental conditions will give full equilibrium.
Phase Reeationships for Adsoreed Layers on Surfaces
Authors: Lu T.-M. , Lagally M. G. 
Published: March 2011

ABSTRACTOrdering phenomena of adsorbed atoms that are commensurate with the substrate structure can be described by a two-dimensional lattice gas. The major features of temperature-coverage phase diagrams for commensurate overlayers are reviewed and illustrated with several experimental examples. For overlayers with net attractive interactions, a two-phase region consisting of ordered overlayer and nearly empty substrate surface forms at low coverage. Substrate extended defects such as steps can create diffusion barriers, thus forming thermodynamic subsystems by eliminating communication between adsorbed atoms on either side of the steps. Steps can also prevent the growth of a reconstructed layer. Experimental examples are presented.
Spin Glassiness and Ferromagnetism in Disordered Ni-Mn Alloys
Authors: Kouvel James S. 
Published: March 2011

ABSTRACTFrom magnetic measurements, the alloy Ni78Mn22 is found to undergo a field-induced transition from spin glassiness to ferromagnetism at a critical field that decreases from ∼140 Oe to zero as the temperature is raised from 4.2 K to 40 K, the ferromagnetic Curie point being ∼270 K. The alloy Ni74Mn26 is found to transform at 80 K from a spin glass to a state of infinite initial susceptibility but no spontaneous magnetization and to remain so up to 155 K, where it becomes paramagnetic. The spin-glass properties of Ni78Mn22 below 40 K and of Ni74Mn26 below 80 K include displaced hysteresis loops produced by cooling in a field. The changes in the hysteresis loops upon subsequent warming correspond to a gradual conversion of a unidirectional anisotropy to a uniaxial anisotropy.
Phase Transformation Under Intense Shock Pressure Loading
Authors: Grady Dennis E. 
Published: March 2011

ABSTRACTSolids subjected to high velocity impact or explosive loading may undergo polymorphic phase transformation or melting within time periods appreciably less than 10-8s due to the intense shock-pressure environment. Although criteria for equilibrium phase transformation on the Hugoniot are satisfied, other nonequilibrium features unique to the shock-wave environment have been identified in the shock transformation process. These features include shear and heterogeneous deformation effects which control the transformation kinetics and microstructure of the transformed material. Transformation under shock loading leads to unusual microstructure in the recovered materials and can result in interesting and useful changes in physical and mechanical properties.
The In–Sn Phase Diagram
Authors: Evans Dain S , Prince Alan 
Published: March 2011

ABSTRACTThe In–Sn system has been redetermined using dta, metallography and X-ray diffraction techniques. It is confirmed that the B and y intermediate 8hases are formed by peritectic reactions, at 141.0° and 222.6°C respectively. β and γ form a eutectic at 47.4 at% Sn and 119°C. The kink in the γ–phase solidus proposed by Heumann and Alpaut is not confirmed.
Modification of Al-Si Microstructure - The Al-Si-Sr Phase Diagram from 0–20 WT. % Si and 0–5.0 WT. % Sr
Authors: Hanna M. D. , Hellawell A. 
Published: March 2011

ABSTRACTIt is well known that the morphology of primary and eutectic silicon resulting from solidification is sensitive to minor impurity additions: “modification” by alkali and alkaline earth metals is common foundry practice and the use of strontium is of recent and current interest because its effect is retained in liquid metal for relatively long times. The mechanism for modification remains obscure and is not necessarily the same from one elemental addition to the next, but it is essential to separate the equilibrium and kinetic influences if the phenomenon is to be better understood. Accordingly, the liquidus surface and eutectic reactions have been located in the relevant part of the Al-Si-Sr system by careful thermal analysis and the results correlated with the microstructure. Comparison is made with the parallel behavior of alkali metal additions.
Phab - An Alloy Phase Diagram Bibliographic Database: A Part of the Asm/Nbs Data Program for Alloy Phase Diagrams
Authors: Cuthill John R. , Baker Hugh 
Published: March 2011

ABSTRACTPHAB is intended to be a complete bibliographic file of the phase diagram data papers pertaining to the experimental determination, evaluation and calculation of phase diagrams of binary, ternary and higher-order alloy systems. Metastable as well as stable equilibrium data, crystal structure, thermodynamic and high pressure data are included. The database will provide a service to the scientific community as well as serving the ASM/NBS Data Program for Alloy Phase Diagrams. The PHAB Database will serve as a source of data to the other activities and outputs of the Program, including alloy system evaluations, the Bulletin of Alloy Phase Diagrams and bound volumes of evaluated phase diagrams. as well as other databases.
Electronic Energy and Short-Range Order in Binary Alloys
Authors: Robbins Mark O. , Falicov L.M. 
Published: March 2011

ABSTRACTAn electronic theory for the total energy of binary alloys is presented. It treats the entire range of concentration and short-range order. The method in not ab initio, but requires only information about the pure elemental constituents of the alloy. Results for two very different metal series, monovalent metals and 4-d transition metals, are calculated and compared to experiment and other models. The model calculation allows us to examine the physical basis for experimental trends.
Quantitative Predictions from Solid-State Physics - What do Phase Diagram Calculators Want?
Authors: Rand Malcolm 
Published: March 2011

ABSTRACTThe types of information required for the calculation of phase diagrams are discussed by considering the computation of typical ternary sections from the constituent binary systems. Such calculations require a knowledge of the Gibbs energy of transformation (lattice stabilities) and Gibbs energies of mixing of wholly metastable, as well as the stable phases in binary systems. Similarly, the stabilities of metastable compounds such as Fe7C3 would be required for computations in the C-Cr-Fe system.These requirements are compared to the information provided by solid-state theoreticians. Essentially such calculations provide enthalpy values at 0 K (or some unspecified temperature for semi-empirical models); however the lattice dynamics and configurational entropy of simple phases have been included in some recent computations. The importance of predicting the entropy and thus heat capacity of metallic phases - particularly metastable phases - is therefore emphasized. Identification of those contributions to the heat capacity which are responsible for the differences between metal polymorphs is discussed, particularly the formalism for magnetic and atomic ordering phenomena. Predictions of ordering temperatures and magnetic moments as a function of composition would be of considerable help for phase diagram calculations.Ab-initio calculations already have considerable success in predicting molar volumes of both stable and metastable phases, so that such information will undoubtedly be of considerable value in studying alloy behaviour at high pressures.
Ductile-Phase Toughening in Niobium-Niobium Silicide Powder Processed Composites
Authors: Nekkanti Rama M. , Dimiduk Dennis M. 
Published: March 2011

AbstractThe Nb-Si system offers a possibility of ductile-phase toughening of the brittle Nb5Si3 intermetallic with the terminal niobium-silicon solid solution. Powder composites have been made in which the volume fraction of the terminal Nb-Si phase is systematically varied in a matrix of Nb5Si3 in order to study the extent of toughening. The Nb-Si solid-solution phase was observed to exhibit cleavage failure under both as hot pressed and heat treated conditions, thereby limiting the toughening attained by the presence of this phase. Hot working of the composite results in a dramatic improvement in toughness because of a change in the plastic behavior and fracture mode of the terminal Nb-Si phase from brittle cleavage to a mixed mode of cleavage and ductile microvoid growth and coalescence (dimpled) fracture.
Ductile-Phase Toughening of Cr3Si with Chromium
Authors: Newkirk Joseph W. , Sago J. Alan 
Published: March 2011

AbstractCr-Si alloys offer important advantages as an aerospace material, including high service temperature and good oxidation resistance. This in-situ composite combines a hard, brittle silicide phase with a softer chromium phase. The soft phase is intended to add damage tolerance. Alloys with high volume percents of the silicide phase had good strength values at temperatures up to 1200C or more. Microhardness indents were used to demonstrate that the chromium phase could act as a crack bridging material. In addition the microstructural stability of these materials was studied with encouraging results.
Simple Measurements of Toughness and Crack Formation in Several Intermetallic-Matrix Composite Systems
Authors: Fleischer Robert L. 
Published: March 2011

AbstractChisel-and-hammer (C.T.) and microhardness tests have been used to examine trends in toughness and crack formation in several intermetallic-based two-phase equilibrium systems. High fracture toughness, as defined by the chisel test, correlates with the presence of some ductility; and the lack of crack formation, or its limitation by a second phase in the microstructure, are prerequisites for fracture resistance. Equilibrium systems have desirable stability for use at elevated temperatures. Comparison of Tbd and C.T. is now possible for a wide range of intermetallics. Intuition suggests that Tbd and C.T. would anti-correlate. Observation, however, contradicts that hypothesis. There are significant numbers of alloys with low Tbd and low C.T. and with high Tbd and high C.T. Possible explanations are noted. Systems that have been studied include Al-Ru with Sc additions, Be-Ti, Be-Zr, Cr-Ti, with Al, Nb and Zr, Ge-Ti, Ir-Nb with Co, Fe, Ni, and V, and Ru-Ta with Co and Fe. Compositional effects on chisel toughness, hardness-vs-temperature, and crack information are presented.
Determination of Fiber/Matrix Interface Mechanical Properties in Brittle-Matrix Composites
Authors: Kerans Ronald J. , Jero Paul D. , Parthasarathy Triplicane A. , Chatterjee Amit 
Published: March 2011

AbstractIt has been evident for some time that the mechanical properties of the fiber/matrix interface play an important role in determining the mechanical behavior of ceramic composites (for reviews, see [1], [2], and [3[). Recently there has been a growing interest in the role of the fiber/matrix interface in intermetallic matrix composites. While ceramic and intermetallic composites are certainly very different materials, understanding the behavior of one will provide insight into the other. Furthermore, the basic issues regarding the determination of interface properties are the same. The accuracy of micromechanics models of any composite system is dependent upon the accuracy of all the constituent and interface properties. It is far preferable to measure actual materials constants rather than test-specific quantities. The tests described here are intended to measure the interfacial shear strength (or mode II toughness) and the interfacial tensile strength. The objective of this work is to briefly outline a few of the approaches which are being evaluated for and applied to ceramic composites, and which may be of interest to investigators working in intermetallic composites.
The Effect of Notches on the Fatigue Life of SCS-6/Ti3Al Composite
Authors: Bain Kenneth R. , Gambone Mary Lee , Zordan Richard D. 
Published: March 2011

AbstractLow cycle fatigue tests were performed on Ti-24Al-11Nb titanium aluminide composite unidirectionally reinforced with SCS-6 fiber. (SCS-6 is a SiC-based fiber manufactured by Textron-SMD in Lowell, Massachusetts.) The effect of circular holes onthe fatigue life of this composite system was measured with respect to fiber orientation, temperature, and frequency. Longitudinal and transverse specimens with and without holes were tested at 26°C and 649°C at 0.33 Hz. In addition, longitudinal specimens were also tested at 30 Hz and 649°C to determine the effect of frequency.A degradation in fatigue life due to the presence of holes was observed in specimens loaded in the fiber direction (longitudinally). This effect is independent of frequency. The notch sensitivity factor, Q, associated with the reduction in life ranges from 0.33 to 0.50 over the range of temperature tested.The specimens oriented with the load axis perpendicular to the fiber direction (transverse) demonstrated no sensitivity of fatigue life to the presence of holes at room temperature but did possess a finite sensitivity at 649°C with a Q=0.45.