Thermodynamic evaluation of the surface tension and viscosity of liquid quaternary alloys: The Ti-Al-Cr-Nb system (original) (raw)
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Surface, dynamic and structural properties of liquid Al–Ti alloys
Applied Surface Science, 2012
The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al-Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al-Ti melts. The study on surface, dynamic and static structural properties of liquid Al-Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al-2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.
Thermodynamics, surface properties and microscopic functions of liquid Al–Nb and Nb–Ti alloys
Journal of Non-Crystalline Solids, 2010
The energetics of mixing in Al-Nb and Nb-Ti liquid alloys have been analysed through the study of surface properties (surface tension and surface segregation), dynamic properties (chemical diffusion) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of statistical mechanical theory in conjunction with quasi-lattice theory (QLT). The phase diagram of the Al-Nb system exhibits three intermetallic compounds in the solid state, while a relatively simple phase diagram of the Nb-Ti system indicates nearly ideal mixing behaviour in the liquid phase and two stable solid phases. Since the structure of a liquid alloy is in some respects similar to that of a crystal, the complex formation phenomenon in Al-Nb melts has been analysed by a quasi-lattice structural model for chemical complexes. The energetics and structural arrangement in Nb-Ti melts have been studied by the quasi-chemical approximation (QCA) for the regular solution model.
Use of Thermodynamic Data to Determine Surface Tension and Viscosity of Metallic Alloys
MRS Bulletin, 1999
During the last three decades, various thermodynamic databases have been compiled to be applied mainly to the calculation of phase diagrams of alloys, salts, and oxides. The accumulation and assessment of thermodynamic data and phase-equilibrium information to establish those databases is sometimes called the CALPHAD (calculated phase diagram) approach. The CALPHAD approach has been recognized as useful in various aspects of materials science and engineering. In addition to the use of thermodynamic databases for the calculation of phase diagrams, it would be very desirable to apply them to the calculation of other physicochemical quantities, such as surface tension. By doing this, not only can the Utility of databases be enlarged, but also a deeper understanding of the physical properties in question can be reached.On the basis of the concepts just mentioned, we have applied those thermodynamic databases to the calculation of the surface tension of liquid alloys and molten ionic mix...
Thermophysical properties of metallic melts and their effects on solidification related processes
2022
Among the thermophysical properties, the surface / interfacial tension, viscosity and density / molar volume of liquid alloys are the key properties for the modelling of microstructural evolution during solidification. Therefore, only reliable input data can yield accurate predictions preventing the error propagation in numerical simulations of solidification related processes. Due to experimental difficulties related to reactivity of metallic melts at high temperatures, the measured data are often unreliable or even lacking. The application of containerless processing techniques either leads to a significant improvement of the accuracy or makes the measurement possible at all. On the other side, accurate model predicted property values could be used to compensate the missing data; otherwise, the experimental data are useful for the validation of theoretical models. The choice of models is particularly important for the surface, transport and structural properties of liquid alloys r...
The partial liquidus projection and solidification sequences in Ti-(40–60) Al-(5–30) Nb alloys
Journal of Alloys and Compounds, 2021
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Materials Science and Engineering A, 2004
The nucleation and growth kinetics of α-Al grains in the systems Al-0.1Ti and Al-0.15TiB 2 (wt.%) have been studied by time-resolved neutron diffraction measurements during the liquid-solid phase transformation under continuous cooling. The evolution of the static structure factor S(Q) was monitored for different cooling rates. The evolution of the solid fraction f S for both samples during the transformation was determined from the normalized variation of the height of first peak in the liquid structure factor. The transformation kinetics was analyzed in terms of the Johnson-Mehl-Avrami model, and compared for both samples. The evolution of Bragg peaks emerging after the nucleation of the solid phase was monitored. The results reveal that the TiB 2 particles in pure aluminum are not effective nucleation sites for α-Al grains during solidification. However, the presence of solute titanium in the Al-0.1Ti alloy changes the growth rate of crystallization during solidification. In the early stages of the phase transformation in the Al-0.1Ti alloy, pronounced oscillations in the Bragg peaks intensity are observed. These observations are discussed in the light of the present grain refinement theories.
The Measurement and Estimation of Density for Selected Liquid Alloys
2017
The simulation modelling of metal processes requires realistic; accurate and self-consistent thermophysical properties as input data. In particular, solidification models have been shown to be sensitive to small changes in the density of the liquid alloy. This paper compiles experimental data for the density of some selected liquid aluminium; magnesium and nickel-base alloys. Comparison with ideal mixing calculations for aluminium and magnesium alloys shows agreement between the calculations and the experimental results within the measurement uncertainties. For nickel alloys there is discrepancy between the ideal model and experiment. These differences are interpreted in terms of the measured non-ideality of mixing of Ni-Al binary alloy and other reported binary interactions.
Surface Properties of Liquid Al-Ni Alloys: Experiments Vs Theory
Microgravity Science and Technology, 2020
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.
Nepal Physical Society, 2017
Theoretical modeling equations are developed by extending regular associated solution model to predict the thermodynamic and structural properties of the liquid Tl−Na alloys at higher temperatures. The thermodynamic properties have been predicted by computing activities of unassociated monomers ( and ) and free energy of mixing ( ) at temperatures 673 K, 773 K, 873 K and 973 K. The structural properties have been predicted by computing concentration fluctuation in long wavelength limit ( ), short range order parameter ( ) and ratio of mutual to intrinsic diffusion coefficients ( ) at aforementioned temperatures. These properties have been then correlated with the modified Butler's model to predict the surface properties, such as surface concentrations of free monomers ( and ) and surface tension ( ) of the alloy at above mentioned temperatures.