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Using the available experimental and literature data, the linear temperature-dependent interaction parameters of liquid binary alloys, subsystems of the Al-Cu-Ni system in the Redlich–Kister (R–K) polynomial form were optimized. The activities of pure components of binary subsystems were then computed using optimized parameters and subsequently validated by available experimental and literature data. The thermodynamic database of the excess Gibbs free energy of mixing for the ternary system was theoretically reproduced for temperatures of 1773, 1873, 1973 and 2073 K, applying general solution model, Toop's and Kohler's geometric models. The goal of this effort is to develop a database of the thermodynamic and thermophysical properties of the system so that it can be conveniently used for future research. Indeed, employing Butler's equations with the partial excess Gibbs free energies as inputs, the surface tensions of binary subsystems were computed. Based on the aforementioned models, using the optimized coefficients of R–K polynomials for the excess surface tensions of binary subsystems, the surface tension of the ternary system was obtained. [ABSTRACT FROM AUTHOR]

The Sm–Ni–Al phase relationships at 800 °C have been investigated by using several well–focused experimental techniques such as X–Ray Powder Diffraction (XRPD), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Microprobe Analysis (EPMA). The isothermal section of the Sm–Ni–Al system at 800 °C was constructed according to the present experimental results. More than 50 alloys have been synthesized and characterized in the 30–100 at.% Al region. At 800 °C, 9 intermetallic phases have been confirmed, characterized and their relationships have been established. In the Al-rich corner, the presence of two ternary invariant reactions have been postulated whilst along the 16.67 at.% Sm isopleth, the presence of two structurally related extended solid solutions have been observed. The determined phase equilibria at 800 °C are discussed and compared with the isothermal section at 500 °C already reported in literature. [ABSTRACT FROM AUTHOR]

Transitions from the liquid to the solid state of matter are omnipresent. They form a crucial step in the industrial solidification of metallic alloy melts and are greatly influenced by the thermophysical properties of the melt. Knowledge of the thermophysical properties of liquid metallic alloys is necessary in order to gain a tight control over the solidification pathway, and over the obtained material structure of the solid. Measurements of thermophysical properties on ground are often difficult, or even impossible, since liquids are strongly influenced by earth's gravity. Another problem is the reactivity of melts with container materials, especially at high temperature. Finally, deep undercooling, necessary to understand nucleus formation and equilibrium as well as non-equilibrium solidification, can only be achieved in a containerless environment. Containerless experiments in microgravity allow precise benchmark measurements of thermophysical properties. The electromagnetic levitator ISS-EML on the International Space Station (ISS) offers perfect conditions for such experiments. This way, data for process simulations is obtained, and a deeper understanding of nucleation, crystal growth, microstructural evolution, and other details of the transformation from liquid to solid can be gained. Here, we address the scientific questions in detail, show highlights of recent achievements, and give an outlook on future work. [ABSTRACT FROM AUTHOR]

A new experimental investigation of the Sb-Sn phase diagram has been performed. Special attention was focused on the phase equilibria within SbSn-Sb3Sn4 composition range. Phase equilibria have been investigated by DSC measurements combined with a thorough optical and electronic microscopy examination with a special attention to the SbSn-Sb3Sn4 phase transformation. Both DSC and metallographic results have been critically evaluated and debated. The presence of two peritectic reactions L + Sb3Sn4 ⇌ (βSn) at 243 ± 1 °C and L + (Sb) ⇌ (SbSn) at 420 ± 1 °C have been confirmed. The invariant reaction at 321 ± 1 °C has been observed and an additional small effect at about 330-340 °C was systematically recorded. These results have been extensively discussed. [ABSTRACT FROM AUTHOR]

The present study is an overview of the surface properties of liquid Al-Ni alloys, which are of great importance for the design and development of new Al-Ni and Ni-based industrial alloys, widely used as functional and structural materials. The solidification and thus, the microstructural evolution are directly dependent on the interface/surface properties of metallic melts. Therefore, numerical simulation of microstructure evolution requires reliable property data as input to such models. Taking into account the experimental difficulties related to a high reactivity of liquid Al-Ni alloys and the effects of impurities on their surface properties, the surface tension over the whole concentration range has been determined in the frameworks of three international research projects. Namely, the surface tension measurements have been carried out by both traditional container-based and as an alternative, containerless methods within the ESA-MAP ThermoProp and ESA-MAP Thermolab Projects and also under the EU FP6-IMPRESS Project. The obtained datasets were analysed and subsequently compared with the model predicted values as well as with the literature data. A strong exothermic mixing characterises the Al-Ni system and the presence of a few intermetallic compounds in the solid state leads to the formation of short range ordered elements or complexes in the liquid phase, at least near the melting temperature, which significantly affects the surface properties of alloy melts. Aiming to estimate the effects of short range ordering on these properties, the Compound Formation Model (CFM) and the Quasi Chemical Approximation (QCA) for regular solution were applied. [ABSTRACT FROM AUTHOR]

The present work is aimed to highlight the interfacial properties (surface tension and wettability) of metallic systems involved in the additive manufacturing processing (AM) and their importance for design and development of new candidate materials as it has been already done in the field of joining processes (soldering, brazing, welding). The surface properties of Al-12.6Si (in wt pct) alloy, taken as a reference alloy of a class of additive manufacturing Al-Si based alloys, were investigated. The contact angles of pure Al and of Al-12.6Si alloy in contact with Al2O3 substrates were obtained by applying the sessile drop method under different working atmospheres. The new reference data on the wetting properties of the Al-12.6Si/Al2O3 system can be useful for design and development of new Al-Si-based alloys to be used in AM. The surface tension and the surface segregation of liquid Al-Si alloys were calculated as functions of composition by using Butler's model and the results obtained were compared to available literature data. [ABSTRACT FROM AUTHOR]

This review represents the state of the art in the thermophysical properties of liquid Ag-Sn alloys highlighting the surface and wetting properties of Ag-Sn eutectic solder. It includes an atomistic approach developed within the framework of statistical mechanical theory in conjunction with a Quasi Lattice Theory that, through a rigorous mathematical formalism, provides exact relationships between the properties in terms of classical thermodynamics. The model predicted property values are substantiated by available experimental data. Based on the phase diagram evidence about the existence of ε-Ag3Sn intermetallic compound, the surface (surface tension and surface composition), transport (viscosity and diffusivity) properties and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) have been studied using the Compound Formation Model in a weak interaction approximation and Quasi Chemical Approximation for regular solutions. A case study of Ag-Sn eutectic alloy is presented. Taking into account its importance for design and development of lead free solder alternatives, the literature data on the wettability and the phases formed at the interface between Ag-Sn eutectic alloy and different substrates (Cu, Ni, Au, Pd) have also been analysed. [ABSTRACT FROM AUTHOR]

The thermophysical properties, e.g., melting range, specific heat, solid fraction, density, and surface tension of four industrial Ni-based alloys, namely MC-2, CMSX-10, TMS-75, and LEK-94, have been determined within the ground-based experiments program of the ESA MAP ThermoProp project. The tests were performed under reducing atmosphere in order to lower the oxygen contamination. The results obtained have been compared with the corresponding data of Ni-based alloys available in literature. The new experimental data have been analyzed as a function of both temperature and alloy composition and interpreted by means of different thermodynamic models. [ABSTRACT FROM AUTHOR]

Experimental determination of thermodynamic and thermophysical properties of both solid and, in particular, liquid alloys at high temperatures is often technically difficult or even impossible, and therefore theoretical models can be used to estimate missing property values. Preliminary inspection of the literature related to the Cr-Nb-Re system and its binary subsystems reveals mainly theoretical results obtained in the framework of different theories, but the corresponding experimental property data are still sparse. The energetics of mixing in liquid Cr-Nb, Cr-Re and Nb-Re systems has been analysed through the study of the concentration dependence of various thermodynamic, surface (surface tension and surface composition) and structural properties (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) by the first or the quasi-chemical approximation for regular solutions, developed by Bhatia and Singh, in the framework of statistical mechanical theory in conjunction with the quasi-lattice theory. The results obtained for these binary systems have been extended to study the thermodynamics and surface properties of ternary Cr-Nb-Re liquid alloys. [ABSTRACT FROM AUTHOR]

Au-Ge-based alloys are potential substitutes for Pb-rich solders currently used for high-temperature applications. In the present work, the wetting behavior of two Au-Ge-X (X = Sb, Sn) ternary alloys, i.e., Au-15Ge-17Sb and Au-13.7 Ge-15.3Sn (at.%), in contact with Cu and Ni substrates has been investigated. Au-13.7Ge-15.3Sn alloy showed complete wetting on both Cu and Ni substrates. Total spreading of Au-15Ge-17Sb alloy on Cu was also observed, while the final contact angle of this alloy on Ni was about 29°. Pronounced dissolution of Cu substrates into the solder alloys investigated was detected, while the formation of Ni-Ge intermetallic compounds at the interface of both solder/Ni systems suppressed the dissolution of Ni into the solder. [ABSTRACT FROM AUTHOR]

u-Ge-based alloys are interesting as novel high-temperature lead-free solders because of their low melting point, good thermal and electrical conductivity, and high corrosion resistance. In the present work, the wetting and soldering behavior of the eutectic Au-28Ge (at.%) alloy on Cu and Ni substrates have been investigated. Good wetting on both substrates with final contact angles of 13° to 14° was observed. In addition, solder joints with bond shear strength of 30 MPa to 35 MPa could be produced under controlled conditions. Cu substrates exhibit pronounced dissolution into the Au-Ge filler metal. On Ni substrates, the NiGe intermetallic compound was formed at the filler/substrate interface, which prevents dissolution of Ni into the solder. Using thin filler metal foils (25 μm), complete consumption of Ge in the reaction at the Ni interface was observed, leading to the formation of an almost pure Au layer in the soldering zone. [ABSTRACT FROM AUTHOR]

The surface tension and density of three liquid AlTi-based alloys (AlTiV, AlTiNb, and AlTiTa) have been measured using electromagnetic levitation as a tool for containerless processing. Surface tension has been determined by the oscillating-drop method, while the density was measured using a shadowgraph technique. Both quantities were determined over a wide temperature range, including the undercooled regime. In addition, sessile-drop and pendant-drop experiments to determine the surface tension were performed in a recently built high-temperature furnace. The measured data were compared to thermodynamic calculations using phenomenological models and the Butler equation. Generally, good agreement was found. [ABSTRACT FROM AUTHOR]

The density and the surface tension of binary Sn–Sb and ternary Sn–Sb–Cu liquid alloys have been measured over a wide temperature range by the sessile-drop method. The experimental data for the surface tension were analyzed by the Butler thermodynamic model. Investigations of the wetting behavior of these alloys on the Cu and Ni substrates in a vacuum were also performed. [ABSTRACT FROM AUTHOR]

Within the Integrated Project IMPRESS, funded by the EU, a concerted action was taken to determine the thermophysical properties of a γ-TiAl-based alloys, suitable for casting of large turbine blades for aero-engines and stationary gas turbines. The challenge was to develop a castable alloy, free of grain refiners and susceptible to heat treatment. Owing to the high reactivity of this class of alloys, many difficulties were encountered to process the liquid phase in a crucible. This prevented also the measurements of specific heat, viscosity and electrical conductivity in the liquid phase. However, surface tension and density could be measured using container-less techniques. For the surface tension determination, both the oscillating droplet method by the electromagnetic levitation as well as a combined method using two methodologies in one test (i.e. the pendant drop and sessile drop) by an advanced experimental complex that has been designed for investigations of high temperature capillarity phenomena were applied. All the quantities have been obtained as a function of temperature, in some cases also in the undercooled liquid. In this article, we report a comparative discussion on the results obtained for the surface tension of Ti–Al–Nb and Ti–Al–Ta alloys, together with the corresponding theoretical values calculated by thermodynamic models. [ABSTRACT FROM AUTHOR]

Surface tension measurements of different alloys of the Al-Ni system, performed both under reduced gravity conditions in parabolic flights and on ground by conventional techniques, are presented. The alloys compositions were selected on the basis of the intrinsic compound forming tendency with the aim to allow a sensitive test of model predictions. [ABSTRACT FROM AUTHOR]

The mixing behaviour of Ga-Sn and Ga-Zn segregating alloy systems has been investigated by the Quasi-Chemical Approximation (QCA) in the frame of the Quasi-Lattice Theory (QLT) combined with a statistical mechanical theory. Assuming the order energy parameters as temperature dependent, various thermodynamic quantities are calculated at different temperatures. Thermodynamic properties of both systems deviate positively from the Raoult’s law. The energetics of mixing in liquid alloys has been analysed through the study of surface properties (surface tension and surface composition) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter). Theoretical results are in a good agreement with the corresponding literature data and support a weak demixing tendency in Ga-Sn and Ga-Zn liquid alloys. [ABSTRACT FROM AUTHOR]

A theoretical model of grain growth in sintering of clustered powder compacts is outlined, showing that the microstructure evolution is stepwise continuous in time and its general trends can be predicted independently of the particular system and process being considered. The dependence of coarsening on densification can be accounted for by introducing a densification-scaled time variable (intrinsic time). The theory is successively applied to systems where particular local mechanisms of matter transport are supposed to operate, respectively in the initial/intermediate and the intermediate/final stage of sintering. The obtained mathematical models are solved numerically to follow the evolution of three regularly packed clusters. The model predictions are in good agreement with experimental data obtained by other researchers. [ABSTRACT FROM AUTHOR]