Atomic mobilities, uphill diffusion and proeutectic ferrite growth in Fe–Mn–C alloys

Following the treatment in CALPHAD, experimental data on diffusivities in Fe–Mn and Fe–C binary systems are critically evaluated with the DICTRA software to derive atomic mobilities. The effect of magnetic ordering on diffusion in bcc phase is taken into account, and the obtained atomic mobilities are expressed as functions of temperature and compositions with the Redlick–Kister polynomials. Based on the mobility parameters obtained in this work for the end-members and the interaction terms, comprehensive comparisons between the calculated and experimentally measured quantities are made. Due to the lack of experimental diffusivities for the ternary system, extrapolation based on binary information is performed, the results of which are used to study uphill diffusion of C in fcc Fe–Mn–C alloys. Such C diffusion against its own concentration gradient is a common occurrence for ternary systems containing one interstitial element, provided that the initial alloy compositions of diffusion couples are well chosen. In addition, the operating tie line evolution for proeutectic ferrite growth is also investigated, where C diffusion-controlled fast and Mn diffusion-controlled slow growths are discussed.     

The thermodynamic analysis of Guinier–Preston zones in aged supersaturated Al–Cu alloys

Being the structural cause of hardening, Guinier–Preston (GP) zones in many alloys still attract much interest. The expression of energy for GP zones in the Al–Cu alloy is established by combining the essential Gibbs energy with the interfacial energy and the strain energy. Based on the equilibrium between GP zones and the surrounding matrix, a quantitative analysis on the sizes, concentrations, aging temperatures and their relationships can be predicted. The size and the concentration of GP zones calculated with defined composition and aging temperature accord with the experimental results well.     

Thermodynamic evaluation of the phase equilibria and glass-forming ability of the Fe–Si–B system

A thermodynamic study has been carried out on the Fe–Si–B ternary system, which is important in the development of transformer core materials and Ni-based filler metals. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by combining the experimental results from differential scanning calorimetry with literature data. The evaluated parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. Furthermore, the glass-forming ability of this ternary alloy was evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies–Uhlmann kinetic formulations. In this evaluation, the time–temperature-transformation (TTT) curves were obtained, which are a measure of the time required to transform to the minimum detectable mass of crystal as a function of temperature. The critical cooling rates calculated on the basis of the TTT curves enabled us to evaluate the glass-forming ability of this ternary alloy. The results show good agreement with the experimental data in the compositional amorphization range.     

Computer-aided thermodynamics of fcc solid ternary Fe–Co–Cr alloys by Knudsen cell mass spectrometry

The fcc solid ternary Fe–Co–Cr alloys have been investigated thermodynamically by means of computer-aided Knudsen cell mass spectrometry. The “Digital Intensity Ratio” (DIR) method has been applied for the determination of the thermodynamic excess properties. The ternary thermodynamically adapted power (TAP) series concept is used for the algebraic representation of the molar excess properties. The corresponding TAP parameters as well as the values of the molar excess Gibbs energies G^E, of the molar heats of mixing H^E, of the molar excess entropies S^E, and of the thermodynamic activities at 1673 K are presented.     

Thermodynamic modeling of the ternary Ce–Fe–Sb system: Assessment of the Ce–Sb and Ce–Fe systems

The two Ce–Sb and Ce–Fe binary systems have been evaluated using the calculation of phase diagram method (CALPHAD). All of the binary compounds are treated as stoichiometric compounds. Solution phases are described with an ordinary substitutional solution model. The model parameters were derived from an optimization procedure using all available experimental data. The reproduction of the thermochemical and phase diagram information is reported in a series of figures and tables.     

On the abilities and limitations of the linear,exponential and combined models to describe the temperature dependence of the excess Gibbs energy of solutions

In this paper the performance of the linear, exponential and combined models to describe the temperature dependence of the excess Gibbs energy of solutions in the framework of the Redlich–Kister model is discussed. The models are not compared to existing Calphad optimized databases, rather they are tested against the 209 binary solid and liquid metallic alloys, for which reliable experimental data exist on the heat of mixing and Gibbs energy of mixing in the handbook of Predel. It was found that the linear model often leads to high-T artifact (artificial inverted miscibility gaps) and the excess Gibbs energy approaches infinity at high temperatures, which seems unreasonable. It was also found that although both the exponential and combined models can in principle lead to low-T artifact (liquid re-stabilization), in real systems it probably does not take place, at least for the “normal” systems (a system is “normal”, if the heat of mixing, excess entropy of mixing and excess Gibbs energy of mixing have the same sign at the temperature of measurement; 86% of all systems are found “normal”). The problem with the exponential model is that it is unable to describe the “exceptional” systems (14% of all systems). It is shown that the combined model is able to describe also these “exceptional” systems, as well. An algorithm is worked out to ensure that the combined model does not run into any high-T or low-T artifact, even when it is used to describe the “exceptional” systems. It is concluded that the T-dependence of the interaction energies for all solution phases described by the Redlich–Kister polynomials should be described by the combined model. In this way an improved databank on excess Gibbs energies of solution phases can be gradually built, not leading to any artifact.     

Construction of modified embedded atom method potentials for the study of the bulk phase behaviour in binary Pt–Rh, Pt–Pd, Pd–Rh and ternary Pt–Pd–Rh alloys

A first attempt is made to simulate the solid part of the phase diagram of the ternary Pt–Pd–Rh system. To this end, Monte Carlo (MC) simulations are combined with the Modified Embedded Atom Method (MEAM) and optimised parameters entirely based on Density Functional Theory (DFT) data. This MEAM potential is first validated by calculating the heat of mixing or the demixing phase boundary for the binary subsystems Pt–Rh, Pt–Pd and Pd–Rh. For the disordered alloy systems Pt–Rh and Pt–Pd, the MC/MEAM simulation results show a slightly exothermic heat of mixing, thereby contradicting any demixing behaviour, in agreement with other theoretical results. For the Pd–Rh system the experimentally observed demixing region is very well reproduced by the MC/MEAM simulations. The extrapolation of the MEAM potentials to ternary systems is next validated by comparing DFT calculations for the energy of formation of ordered Pt–Pd–Rh compounds with the corresponding MEAM energies. Finally, the validated potential is used for the calculation of the ternary phase diagram at 600 K.     

Assessment of diffusion mobilities in FCC Cu–Ni alloys

On the basis of the available thermodynamic parameters and experimental data of tracer diffusivity, intrinsic diffusivity and chemical diffusivity in the Cu–Ni binary system, the atomic mobilities of Cu and Ni in face-centered cubic (fcc) Cu–Ni alloys have been assessed as a function of temperature and composition using the CALPHAD approach and DICTRA software package. Comparisons between the calculated and measured diffusion coefficients show that most of the experimental information can be reproduced satisfactorily in the present work. The obtained mobility parameters can also predict reasonably the concentration profiles of the diffusion zone in binary Cu–Ni diffusion couple.     

Assessment of the diffusional mobilities in the face-centred cubic Ag–Zn alloys

Based on the available thermodynamic information and diffusion coefficient data of the Ag-Zn binary system, the atomic mobilities of Ag and Zn in face-centred cubic (fcc) Ag-Zn alloys have been assessed as a function of temperature and composition in terms of the CALPHAD method using the DICTRA software package. Optimized mobility parameters are presented. Comparisons between the calculated and measured diffusion coefficients show that most of the experimental information can be satisfactorily reproduced in the present work. The obtained mobility parameters can also predict reasonable concentration profiles of the diffusion zone in the binary Ag-Zn diffusion couples.     

Thermodynamic assessments of the Ni–Pt and Al–Ni–Pt systems

The Ni–Pt system is assessed using the CALPHAD method. The four fcc-based phases, i.e. disordered solid solution phase, Ni₃Pt–L1₂, NiPt–L1₀ and NiPt₃–L1₂, are described by a four-sublattice model. The calculated thermodynamic properties and order/disorder phase transformations are in good agreement with the experimental data. In order to facilitate the assessment, first-principles pseudopotential calculations are also performed to calculate the enthalpy of formation at 0 K, and comparison with the assessed values is discussed. By combining the assessments of Al–Ni and Al–Pt, the Al–Ni–Pt ternary system is assessed within a narrow temperature range, focusing on the fcc-based phases and their phase equilibria with B2 phase.     

The experimental study of the Bi–Sn, Bi–Zn and Bi–Sn–Zn systems

The binary Bi–Sn was studied by means of SEM (Scanning Electron Microscopy)/EDS (Energy-Dispersive solid state Spectrometry), DTA (Differential Thermal Analysis)/DSC (Differential Scanning Calorimetry) and RT-XRD (Room Temperature X-Ray Diffraction) in order to clarify discrepancies concerning the Bi reported solubility in (Sn). It was found that (Sn) dissolves approximately 10 wt% of Bi at the eutectic temperature.

The experimental effort for the Bi–Zn system was limited to the investigation of the discrepancies concerning the solubility limit of Zn in (Bi) and the solubility of Bi in (Zn). Results indicate that the solubility of both elements in the respective solid solution is approximately 0.3 wt% at 200 C.

Three different features were studied within the Bi–Sn–Zn system. Although there are enough data to establish the liquid miscibility gap occurring in the phase diagram of binary Bi–Zn, no data could be found for the ternary. Samples belonging to the isopleths with w(Bi) 10% and w(Sn) 5%, 13% and 19% were measured by DTA/DSC. The aim was to characterize the miscibility gap in the liquid phase. Samples belonging to the isopleths with w(Sn) 40%, 58%, 77/81% and w(Zn) 12% were also measured by DTA/DSC to complement the study of Bi–Sn–Zn. Solubilities in the solid terminal solutions were determined by SEM/EDS. Samples were also analyzed by RT-XRD and HT-XRD (High Temperature X-Ray Diffraction) confirming the DTA/DSC results for solid state phase equilibria.     

Computational screening and design of S100B ligand to block S100B–p53 interaction

The binding of S100B to p53 disables the biological function of p53 as a tumor suppressor and thus causes cancer. It is very important to explore the interaction between S100B and p53 and to develop inhibitors to block the interaction in anti-cancer development. In this work, the interaction of S100B to p53 was studied using molecular dynamics (MD) at the atomic level and organic molecules have been identified as potential inhibitors to block the S100B–p53 interaction. It was indicated in the simulations that S100B residues around GLU45 and GLU46 play an important role in the binding of S100B to p53. The three dimensional structure of S100B obtained from S100B–p53 complex (PDB ID: 1DT7) was used as the target protein receptor. Multiple LUDI screenings for S100B ligands were performed using different searching radii 6.23 Å, 7.23 Å, 8.23 Å, 9.23 Å and 10.23 Å with a searching center which was defined as the geometrical center of S100B residues that are within 5 Å from the p53 C-terminal peptide in the complex. Potential organic compounds were screened from the ZINC database using LUDI program implemented in Cerius2 package and evaluated as potential S100B ligands to block the S100B–p53 interaction. The top-scored compounds were selected for binding affinity calculation. The results show that these top-scored ZINC compounds bind in the location where p53 binds and interact with S100B in a similar fashion as p53, and therefore it is expected that they have the potential to block S100B from binding to p53. The ADME and toxicity properties of the potential S100B ligands were also evaluated.     

Atomic mobilities and diffusional growth in solid phases of the V–Nb and V–Zr systems

In conjunction with the thermodynamic parameters in the literature, the atomic mobilities of the V–Nb and V–Zr bcc alloys were assessed from experimental diffusion coefficients. The assessed atomic mobilities are given as functions of temperatures and composition in the CALPHAD format. Comparisons between the calculated and experimental quantities show that the obtained mobility parameters enable most of the experimental diffusion data to be well reproduced. Based on the velocity constructions for lattice planes in V/Nb diffusion couples, the displacements of Kirkendall makers were investigated under various annealing conditions, and the results are in general agreement with experimental values. In addition, computational studies of V/Zr diffusion couples were carried out for the kinetic behaviors of V ₂Zr at various annealing temperatures, from which the temperature dependence of the interdiffusion coefficients for V ₂Zr was evaluated.