Theoretical calculation of eutectic temperature and composition in iron-carbon base ternary and multicomponent alloys

Changes in the stable and metastable eutectic temperatures and compositions of the iron-carbon system by addition of alloying elements were calculated on the basis of the geometrical thermodynamics. The influences of alloying elements on these temperatures and compositions exhibit periodicities. The periodicities of the influences on the stable and metastable eutectic temperatures have a maximum in raising these temperatures, and the periodicities of the influences on the eutectic compositions have a maximum in lowering them, in each periodic row. The calculation of eutectic temperatures was extended to Fe-C base multicomponent alloys, and the calculated eutectic temperatures Were in good agreement with experimental ones given by Oldfield.     

Modeling of gas porosity and microstructure formation during dendritic and eutectic solidification of ternary Al-Si-Mg alloys

A two-dimensional(2-D)multi-component and multi-phase cellular automaton(CA)model coupled with the Calphad method and finite difference method(FDM)is proposed to simulate the gas pore for-mation and microstructures in solidification process of hypoeutectic Al-Si-Mg alloys.In this model,the pore growth,and dendritic and eutectic solidification are simulated using a CA technique.To achieve the equilibrium among multiple phases during ternary Al-based alloy solidification,the phase transition thermodynamics and kinetics are evaluated by adopting the Calphad method.The diffusion equations of hydrogen and two solutes are solved by FDM.The developed CA-FDM coupled model can be used for sim-ulating the evolution of gas microporosity and microstructures,involving dendrites and irregular binary and ternary eutectics,of ternary hypoeutectic Al-Si-Mg alloys.It has the capability of reproducing the interactions between the hydrogen microporosity formation and the growth of dendrites and eutectics,the competitive growth among the growing gas pores of different sizes,together with the time-evolving concentration fields of hydrogen and solutes.The simulated morphology of gas pore and microstructure has a good agreement with the experimental observation.The influences of the initial hydrogen concen-tration and cooling rate on the microporosity formation are investigated.It is found that the main portion of porosity formation occurs in the eutectic solidification stage through analyzing the profiles of porosity percentage and solid fraction varying with solidification time.The varying features of simulated porosity percentage,the maximum and average pores radii indicate that increasing initial hydrogen concentration promotes the formation of higher final porosity percentage and larger pores,while the size of gas pores will significantly reduce with increasing cooling rate,leading to a lower final porosity percentage.     

Stable solute boundary layer for liquid and volume change during eutectic solidification of spheroidal graphite iron

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Experimental determination of solid–liquid interfacial energy for succinonitrile solid solution in equilibrium with the succinonitrile–(D) camphor eutectic liquid

The equilibrated grain boundary groove shapes for Succinonitrile (SCN) solid solution in equilibrium with the Succinonitrile (SCN)–D Camphor (DC) eutectic liquid were directly observed. From the observed grain boundary groove shapes, the Gibbs–Thomson coefficient and solid–liquid interface energy for SCN solid solution in equilibrium with the SCN–DC eutectic liquid has been determined to be (5.39 ± 0.27) × 10⁻⁸ K m and (7.88 ± 0.79) × 10⁻³ J m⁻² with present numerical method and Gibbs–Thomson equation, respectively. The grain boundary energy of SCN rich phase of the SCN–DC eutectic system has been determined to be (14.95 ± 1.79) × 10⁻³ J m⁻² from the observed grain boundary groove shapes. Thermal conductivity ratio of the liquid phase to the solid phase for SCN–0.16 mole % DC alloy has also been measured.     

Thermophysical properties of polyvalent metals and their alloys in the solid and liquid states

Resistivity, thermal conductivity, and ultrasound velocity for the metals of the third group, namely, gallium, indium, and thallium are given in a temperature range from 300 to 1000°K as well as resistivity and thermal conductivity of indium-thallium and thallium-tin alloy systems in wide temperature and concentration ranges.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 4, pp. 614–620, April, 1980.     

Application of vibrational parameters to locate the solid/liquid interface during solidification and melting of metals

A method to locate the solid/liquid interface with vibrational parameters during solidification is proposed for the first time. The sufficient difference in resistance to shear stresses between liquid and solid phases of metals and alloys permits the application of vibrational parameters to locate the interface in real time and in a situation during solidification. Based on the solidification theory, continuum mechanics, vibrational modal analysis and sensitivity analysis, the mechanical model and the dynamic equations of a typical Bridgman solidifying system have been established, the sensitivity of eigenvalues of the Bridgman system to the location of the solid/liquid interface has been derived, and the formulae concerned calculated. The experimental results are in good agreement with the computed ones.     

Benchmark problems and testing of a finite element code for solidification in investment castings

Owing to an increased interest in numerical (finite element and finite difference) simulation of solidification in commercial investment castings, there is a need for proper evaluation of candidate codes. This paper presents a systematic selection of several benchmark problems designed to test modelling of latent heat release in pure metals and superalloys, thermal resistance at the metal/mould interface, temperature dependent material properties and far field radiation. For purpose of demonstration, these problems were analysed with a 2-dimensional finite element code, TOPAZ, available in the public domain; one problem was analysed with its 3-dimensional counterpart, TOPAZ3D, also. The numerical experimentation in the course of this study resulted in several findings of practical value, which are highlighted in the paper.     

Free-energies of the Ti-Ni,Fe-Ni and Mo-Ni alloys in relation to their behaviour under particle irradiation

The metastable free-energy diagrams of the Ti-Ni, Fe-Ni and Mo-Ni systems were calculated at room temperature using a semiempirical theory based on thermodynamic considerations. Ti-Ni and Mo-Ni form equilibrium-ordered compounds that are destabilized by particle irradiation. Effectively, Ti₂Ni, TiNi, MoNi and MoNi₃ amorphize after irradiation. In the present work, this experimental behaviour is understood by considering the modification of the free-energy diagrams after particle irradiation. Conversely, in the Fe-Ni system, a metastable f c c solid solution evolves under irradiation towards ordered FeNi. In this system, according to our calculation, the free-energy of the amorphous phase is much higher than the free-energy of any other competing phase, so the amorphous phase cannot be produced. Each selected alloy has an intermetallic compound (TiNi₃, FeNi₃ and MoNi₄) which does not amorphize by particle irradiation and whose composition is close to the nickel-rich end of the phase diagram. According to the calculated free-energy diagrams, the reason for this impossibility of amorphization would be the competition of the terminal solid solution with the amorphous phase.     

Dynamics of solidification and development of morphology of Cu‐base alloys with a metastable miscibility gap in the range of the undercooled melt

The Cu‐Co system shows a metastable miscibility gap in the range of the undercooled melt. In this work the method of electromagnetic levitation (EML) and drop tube experiments have been used to examine the metastable state of Cu‐Co alloys. The experiments show that both methods allow deep undercooling of the melt into the range of the miscibility gap. Due to the deep undercooling the velocity of the solidification front is very high and the actual microstructure is frozen in. The process of demixing can be observed and the binodal has been determined with high precision. The microstructure of samples processed in the electromagnetic levitation shows an influence of the electromagnetic stirring due to the induction of electric currents into the melt. Drop tube experiments, which lead to a rapid solidification under reduced gravity conditions, in contrary result in a homogeneous distribution of spherical particles of the minority phase. For this reason space experiments under microgravity conditions in the TEMPUS facility are under consideration. In these experiments the stirring effect would be greatly reduced compared to the EML.     

Soft X-ray emission spectroscopy as a tool for studying hydriding behaviors and equilibrium properties of zirconium,zirconium alloys and their hydrides

L-emission spectra from zirconium, zirconium-based alloys and their hydrides are recorded, and empirical measures for the electron densities of d symmetry at the zirconium sites are derived. Hydrogen in these samples are covalently bound to zirconium, and the energetic features of the Zr 4d - H 1s bondings govern the stabilities of the hydrides. The positive relationship between the cell dimensions of an alloy and the stability of its hydride is well understood in terms of the d - H 1s bondings together with the d-d interactions in the starting alloy.     

Comparative study of pharmacokinetic parameters between clarithromycin and erythromycin stearate in relation to their physicochemical properties

Pharmacokinetic parameters for clarithromycin (CAM) and erythromycin stearate (EMS) were obtained from a model including decomposition in the gastrointestinal tract. To confirm the accuracy of the parameters, various physicochemical properties of both drugs were examined. The ratio of the in vivo dissolution rate, the in vivo decomposition rate and the absorption rate between CAM and EMS were well correlated to the ratio of the in vitro intrinsic dissolution rate, the decomposition rate in the acidic solution, and partition coefficient, respectively. One of the reasons for the excellent absorption of CAM compared with that of EMS was the higher stability in the acidic solution and the higher partition coefficient of CAM. These findings indicate that the ratio of the partition coefficient to the decomposition rate constant in acidic solution plays an important role in determining drug bioavailability for macrolide antibiotics.     

Calculation of turbulent momentum transfer in a solid phase based on equations for the second and third moments of particle-velocity pulsations

A chain of transfer equations for the second and third moments of dispersed-phase-velocity pulsations in the anisotropic field of energy of random particle motion is obtained based on the computational procedure developed. The interphase and interparticle interactions are allowed for. The turbulent characteristics of the gas are calculated on the basis of a one-parameter turbulence model generalized to the case of two-phase turbulent flows. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 60–70, March–April, 2007.     

Green's functions for the Laplace equation in a 3-layer medium,boundary element integrals and their application to cathodic protection

We report in this paper a set of nine Green's functions for the Laplace equation for an infinite 3-layer medium in which a layer of finite width is sandwiched between two semi-infinite domains. Typical 3D plots of these Green's functions are computed and presented. Taking an offshore platform as a prime example of a structure in a 3-layer medium (atmosphere, ocean and soil), we work out the boundary element integrals using macro elements such as the tubulars. Constant elements reduce several of these boundary integrals to analytical forms. As an application, we discuss the cathodic protection modelling of offshore structures using the ‘boundary element method’.     

PVT Measurements on tetrafluoroethane (R134a) along the vapor-liquid equilibrium boundary between 288 and 373 K and in the liquid state from the triple point to 265 K

For the investigations of the gas-liquid phase equilibria, a new apparatus has been developed capable of simultaneously determining the pressure and the liquid and vapor densities using Archimedes' principle. The relative measurement uncertainties of the liquid and vapor densities of R134a (purity, 99.999%) at 313 K are 2×10^–4 and 7×10^–4, respectively (95% confidence level). For the measurements in the liquid region along nine quasi-isochores at pressures up to 5 MPa, an isochoric apparatus was used. The relative measurement uncertainty ofpv/(RT) is less than 1×10^–3. In addition to the investigation of the (p, v, T) properties, the temperature and pressure at the triple point and the vapor pressure between the triple point and 265 K were measured. On the basis of these data, a vapor pressure correlation has been developed that reproduces the measured vapor pressures within the uncertainty of measurement. The results of our measurements are compared with a fundamental equation for R134a, which is based on the measurements of other research groups.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Relationship between subjective preference and alpha-wave activity in relation to temporal frequency and mean luminance of a flickering light

Human cortical responses corresponding to the subjective preference for a flickering light under varying temporal frequency and mean luminance were investigated. Paired-comparison tests were performed to examine the subjective preference for a flickering light, and electroencephalograms (EEGs) were recorded from six electrodes (10-20 International Electrode Placement System) during presentations of the most-preferred and least-preferred flickering lights. The results showed a positive correlation between subjective preference and the effective duration of the autocorrelation function of the alpha waves measured at the visual cortex (O1 and O2 electrodes).