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The continuous cooling transformation (CCT) curve of a new type of high speed steel (HSS) for rollers was determined along with its typical microstructures. The CCT curve established shows that the Ac 1 of the steel is 770∼830 °C, the Ac m is 920 °C and the starting temperature of martensite transformation is 190 °C. The Fe–C isopleths, mass fractions of all the phases and mole fractions...
The CALPHAD (Calculation of Phase Diagrams) framework to calculate the thermodynamic properties of multicomponent systems is extended to account for the change in thermodynamic properties by the size effect in small particle systems. We have applied this framework to the CeO 2 –CoO binary in order to elucidate the “liquid phase sintering like” fast densification at unusually low temperatures...
Based on critically reviewed experimental diffusion data available in the literature, atomic mobilities of Fe, Si, Cu and Zn in bcc_A2 Fe–Cu, Fe–Si and Fe–Zn alloys were assessed as a function of temperature and composition by means of DICTRA simulation package. Semi-empirical correlations were used to obtain the self-diffusivities of Cu, Si and Zn in the metastable bcc_A2 phase. Comprehensive comparisons...
A thermodynamic model of the V–Zr binary system is established by CALPHAD approach combined with first-principles calculations. The predicted Gibbs free energies of the compound V 2 Zr and other end-members in the sublattice model for the V 2 Zr phase by the first-principles calculations are used to describe the lattice stabilities of this phase. A set of model parameters for the V–Zr...
A thermodynamic optimization of the La–Zn system is carried out using the CALPHAD (CALculation of the PHAse Diagram) method. This new assessment takes into account the latest experimental values of enthalpies of formation reported in literature. The solution phases (liquid, bcc-La, fcc-La, dhcp-La and hcp-Zn) are modelled as substitution solutions using the Redlich–Kister equation. Nine intermediate...
Thermo-kinetic simulation of precipitate evolution during long-term thermal exposure in ferritic–martensitic heat-resistant power plant steels (P91 and P92) is carried out using MatCalc software, in combination with a Gibbs energy database and a mobility database for steels that come with MatCalc. MX and M 23 C 6 are predicted to remain as major precipitates during long-term thermal...
Phase equilibria and thermodynamic properties in the La–Ni–Cu ternary system were studied by coupling thermodynamic modeling and experimental validation. A set of self-consistent thermodynamic descriptions for phases in the La–Ni–Cu system were obtained on the basis of those three constituent binary and ternary experimental data in the literature. The isothermal section at 673 K and the mixing enthalpy...
Based on a first-principles calculation, the effects of lattice vibration on the segregation behavior of Pt–Rh alloy nanoparticles is examined. Pt atoms naturally have lower vibrational free energy for sites with lower coordination number, while Rh atoms neighboring to the Pt atoms also have lower vibrational free energy with respect to Rh metal nanoparticles. Due to the substantial decrease in vibrational...
It is increasingly important in the context of high-manganese steels of the kind that lead to twinning-induced plasticity to be able to estimate the temperature at which ε-martensite forms when austenite is cooled. We find that the thermodynamic method used in similar calculations for α′ martensite cannot in many cases be implemented because of apparently imprecise thermodynamic data, a conclusion...
CALPHAD kinetics has gained rapid development in recent years, due to its wide applications in engineering novel alloys. In order to simulate the diffusion problems of interest, high-quality atomic mobilities are indispensable. Based on the thermodynamic descriptions for the Mo–Ta, Mo–W, and Mo–Nb binary systems, the atomic mobilities for such alloys are inversely parameterized in this work, including...
In this paper, a previously proposed numerical model for binary alloy solidification, and the corresponding algorithm for solving the strong coupling among the solidification temperature, solid fraction, and liquid composition (T–fS–CL), are extended to ternary alloys. The feasibility of the extended numerical method is demonstrated by sample simulations for the directional solidification of blade-like...
The total energies of intermetallic compounds in the Si–Zr system are calculated employing electronic density-functional theory (DFT). The calculated zero-temperature lattice parameters and internal parameters of the stable intermetallic compounds agree well with those obtained experimentally at ambient temperature. The calculated formation enthalpies are in good agreement with the most recent available...
During alloy and process design, it is often desired to identify regions of design or process variables for which certain calculated functions have optimal values under various constraints, for example, compositions of minimum liquidus temperature in an N-component alloy; compositions where the amount of precipitate in a given phase is maximized or minimized during annealing or rolling; other calculated...
This paper performed thermodynamic calculations on the CeBr 3 compound and the MBr–CeBr 3 binary system over the entire temperature and composition range. The Gibbs energy of CeBr 3 was evaluated using an independent polynomial to fit the experimental heat capacity, a two sub-lattice ionic solution model (M + ) P : (Br − ,CeBr 6−3 ,CeBr...
In order to extend the CALPHAD technique to nanosystems, the thermodynamic description involving the particle size and the shape factor was presented and employed in the calculation of the phase diagram of the Ag–Cu nanosystem.
We propose a cluster expansion (CE) technique that can be applied to any atomic arrangement on alloy systems in their polymorphs. The proposed CE introduces virtual vacancy sites in the starting structure in order to describe the atomic positions for a variety of lattices. We derive the general condition for obtaining effective interactions in the present CE, which results in rigorous expansion of...
The CALPHAD technique has been utilized to study the diffusion characteristics and atomic mobilities in fcc Au–Pt alloys, where the thermodynamics and kinetics descriptions are concurrently taken into consideration. For the investigated atomic mobilities, the end-members and interaction parameters are explored with the impurity diffusion coefficients, intrinsic diffusion coefficients and interdiffusion...
A thermodynamic description for the Nb–Si–Sn system has been developed on the basis of the constituent binaries and critically reviewed ternary experimental data. The published thermodynamic descriptions for the Nb–Si and Nb–Sn binaries were directly used and that for the Si–Sn binary was remodeled in the present study. A two-sublattice model, (Nb,Si,Sn) 3 (Nb, Si, Sn), was applied to the...
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