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To explore diffusion behavior of fcc phase in the Ni-Al-Nb ternary system, binary and ternary alloys were prepared by induction melting to make diffusion couples which were annealed at 1473 K for 50 h. The interdiffusion coefficients were evaluated from the common compositions of two independent diffusion paths, which were then combined with the thermodynamic description to inversely determine the atomic mobilities of Ni, Al and Nb in DICTRA. Comparations between calculated and experimentally-measured interdiffusivities and diffusion profiles in diffusion couples were made, the results of which demonstrate the quality of atomic mobilities obtained in this work. [ABSTRACT FROM AUTHOR]

In this work, diffusion couples of fcc Cu–Cr–Ni alloys annealed at 1373 K for 80 h are investigated. The interdiffusion coefficients are retrieved from common compositions of two diffusion couples, which are then combined with thermodynamic descriptions to explore atomic mobilities of Cu, Cr and Ni in fcc Cu–Cr–Ni alloys within the CALPHAD framework. In order to confirm the quality of such kinetic characteristics, a comparison between calculated and experimentally measured concentration profiles of diffusion couples and diffusion paths in Gibbs triangle is made, where the agreement is excellent. The results of this study contribute to the establishment of a general Ni-based mobility database for alloy design. [ABSTRACT FROM AUTHOR]

Diffusion couples for fcc Cu–Fe–Co ternary system are prepared, all of which are annealed at 1573 K for 50 h. Interdiffusion coefficients are evaluated at the intersection points of two independent diffusion paths sharing a common composition. Such main and cross interdiffusion coefficients are then used to inversely retrieve atomic mobilities of Cu, Fe and Co in fcc Cu–Fe–Co alloys, with the aid of available thermodynamic description. Further validation concerning the quality of atomic mobilities is conducted with computational simulations for diffusion couples, the results of which are compared with experimental data. This work contributes to the establishment of a general Co-based kinetic database for computational design of superalloys. [ABSTRACT FROM AUTHOR]

In order to establish a general Ni-based mobility database, diffusion couples for Ni–Fe–Ti ternary systems are prepared, all of which are annealed at 1573 K for 50 h. Interdiffusion coefficients are retrieved from the common compositions of two independent diffusion paths, which are then combined with thermodynamic description to inversely explore atomic mobilities of Ni, Fe and Ti around the Ni-rich region. Good agreements are obtained from comprehensive comparisons between calculated and experimental diffusion coefficients and concentration profiles, which can be used to verify the quality of atomic mobilities obtained in this work. [ABSTRACT FROM AUTHOR]

Diffusion couples for fcc Co–Cr–Ni ternary system are prepared, all of which are annealed at 1573 K for 50 h. Interdiffusion coefficients are evaluated at the intersection points of two independent diffusion paths sharing a common composition. Such main and cross interdiffusion coefficients are then used to inversely retrieve atomic mobilities of Co, Cr and Ni in fcc Co–Cr–Ni alloys, with the aid of available thermodynamic description. Further validation concerning the quality of atomic mobilities is conducted with computational simulations for diffusion couples annealed at 1573 K for 50 h, the results of which are compared with experimental data. This work contributes to the establishment of a general Co- or Ni-based kinetic database for computational design of superalloys. [ABSTRACT FROM AUTHOR]

Cu–Co–Ni diffusion couples are studied at 1273 K, the composition profiles of which are used to extract interdiffusion coefficients as functions of composition. Such values are further combined with thermodynamic description to extract atomic mobilities of Cu, Co and Ni in order to establish a general Co-based or Ni-based mobility database. The quality of Cu, Co and Ni atomic mobilities are verified through extensive comparisons between calculated and experimentally measured concentration profiles in diffusion couples and diffusion paths in Gibbs triangle. [ABSTRACT FROM AUTHOR]

Abstract: Based on various kinds of diffusivities as well as the thermodynamic descriptions within the CALPHAD framework, the atomic mobilities of U, Ti, Nb and Mo are explored in this work with the DICTRA software. The mobility end-members are evaluated from the impurity diffusivities as well as the extrapolated interdiffusivities, while the interaction parameters for atomic mobilities are determined from the tracer diffusivities, the intrinsic diffusivities and the interdiffusivities. The reliability of such purely kinetic quantities is carefully verified by the comparison between the calculated and experimentally measured quantities, including the concentration profiles in Ti/U diffusion couples. This work is established to provide fundamental information for U-based alloy design when the kinetics of microstructure evolution is of prime concern. [Copyright &y& Elsevier]

Abstract: 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 coefficients. Concentration curves in diffusion couples are computationally studied, the results of which are compared with the experimental values. In addition, the shift and distribution of Kirkendall markers are brought into discussion, based on the intrinsic diffusivities described in the lattice-fixed frame of reference. [Copyright &y& Elsevier]

Abstract: 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 the mobility end-members as well as the interaction parameters. Due to the large experimental errors for diffusion characteristics of refractory alloys at high temperatures, the experimental data are quite scattered. However, this work allows such data to be carefully selected and a set of self-consistent atomic mobilities to be well established, which can be used to study diffusion-related characteristics for Mo-based refractory alloys. [Copyright &y& Elsevier]

Abstract: CALPHAD kinetics has evolved to be a well-established discipline, which allows complex non-equilibrium processes to be fully explored. Such a success relies on the use of Redlich–Kister polynomials to describe atomic mobilities, with the effect of temperature, composition, magnetic ordering and chemical ordering sufficiently taken into consideration. There is thus an increasing demand to construct high-quality atomic mobility databases for alloys of interest. Based on the CALPHAD framework, the atomic mobilities in fcc Cu–Ag–Au alloys are reported in this work, the results of which can provide fruitful information on alloy design. [Copyright &y& Elsevier]

Abstract: Based on the thermodynamic description, the atomic mobilities of Cu, Fe and Ni are inversely parameterized from the experimental data on tracer diffusion and interdiffusion. The quality of atomic mobilities obtained in the present work has been verified through extensive comparisons between the calculated and measured tracer diffusion coefficients, interdiffusion coefficients, concentration profiles and diffusion paths in ternary Cu–Fe–Ni alloys. With such thermodynamic and kinetic descriptions of fcc Cu–Fe–Ni alloys, it is convenient to computationally study the presence and evolution of zero-flux planes (ZPFs) with respect to the lattice-fixed frame of reference as well as the number-fixed frame of reference, the results of which shed light on novel Cu-based and Fe-based alloy design for industry. [Copyright &y& Elsevier]

Abstract: In order to assist the design of bcc Ti–Ta and Ta–W alloys, the atomic mobilities of Ti, Ta and W are studied critically with the DICTRA software (DIffusion Controlled TRAnsformation), based on the published thermodynamic description, self-diffusion coefficients, impurity diffusion coefficients, intrinsic diffusion coefficients and interdiffusion coefficients. Good agreement is obtained from the comprehensive comparisons between the calculated and measured diffusion coefficients. To further verify the obtained atomic mobilities, the concentration profiles and Kirkendall marker shift in bcc Ti–Ta and Ta–W diffusion couples are explored computationally, the results of which can reproduce satisfactorily the experimental measurements. [Copyright &y& Elsevier]

Abstract: Based on the CALPHAD technique, the atomic mobilities and diffusivities in fcc Fe–X (X=Ag, Au, Cu, Pd and Pt) alloys have been critically studied. The thermodynamic descriptions and various types of diffusivities are concurrently taken into consideration using the Dictra software. The obtained mobility end-members and interaction parameters enable a great majority of measured diffusion coefficients to be satisfactorily represented. In addition, the concentration profiles in some binary diffusion couples can be well predicted. This work contributes to the establishment of a comprehensive kinetic description for mobilities in Fe-based alloys, which can address important issues in microstructure evolution in heat treatments. [Copyright &y& Elsevier]

Abstract: Based on the experimental data available in the literature, the mobility end-members for impurity diffusion of twelve elements, i.e. Ag, Al, As, Au, Cu, Mo, Nb, Sb, Sn, Ti, W and Zn, in bcc Fe have been critically studied. The effect of ferromagnetic ordering is taken into consideration, which allows the dramatic change of kinetic behaviors around the Curie temperature to be considered. Comprehensive comparisons between the calculated and experimentally measured impurity diffusion coefficients are made, where the good agreement confirms not only the parameters obtained in this work but also the model developed by Jönsson. This work contributes to the establishment of a general mobility database to computationally study microstructure evolution upon heat treatment and performance prediction during service. [Copyright &y& Elsevier]

Abstract: The mobilities and diffusivities in fcc Co–X (X=Ag, Au, Cu, Pd and Pt) alloys have been critically assessed by the CALPHAD method, based on the reported experimental data and published thermodynamic parameters. The atomic mobilities are expressed as functions of temperature and compositions in the CALPHAD format. Comprehensive comparisons between the calculated and measured diffusivities, such as self-diffusivities, impurity diffusivities, intrinsic diffusivities, and interdiffusivities, are made, where the proposed mobility parameters for Ag, Au, Co, Cu, Pd and Pt enable most of the experimental values to be reproduced. The effect of magnetic ordering on diffusion in fcc Co–Pd and Co–Pt alloys is discussed. This work contributes to the establishment of a Co mobility database, which can aid the computational study of microstructure evolution in Co-based alloys at high temperatures. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Based on the thermodynamic parameters and various experimental diffusion data available in the literature, the atomic mobilities of Ti and Nb in bcc Ti–Nb alloys are critically evaluated with respect to temperatures and compositions in terms of the CALPHAD method. The finally obtained mobility parameters are presented, and extensive comparisons between the calculated and experimentally measured quantities are made. The results show that the obtained mobility parameters can satisfactorily reproduce most of the experimental results, and therefore they can be safely used in diffusion-related simulations to deal with practical problems of interest. In addition, the obtained mobilities, together with the published thermodynamic information, are successfully applied to model the movement of Kirkendall markers in the Ti/Nb diffusion couples. [Copyright &y& Elsevier]

Abstract: The atomic mobilities of Ti and V in bcc Ti–V alloys are critically assessed with respect to temperatures and compositions by the CALPHAD method, where self-diffusion coefficients, impurity diffusion coefficients, tracer diffusion coefficients, interdiffusion coefficients, concentration curves and thermodynamic parameters are employed simultaneously in an optimization process. Comparisons between the calculated and experimentally measured quantities are made. The obtained mobility parameters are used to predict the marker movement behavior, and the result shows a good agreement with the literature information. It is believed that this work contributes to the construction of a general Ti mobility database, which can provide useful guidance for many heat treatment processes. [Copyright &y& Elsevier]

Abstract: On the basis of the available thermodynamic parameters, the atomic mobilities of Nb and Zr in bcc Nb–Zr alloys are critically assessed as functions of temperatures and compositions by the CALPHAD method, where self-diffusion coefficients, impurity diffusion coefficients, tracer diffusion coefficients, interdiffusion coefficients and concentration curves are simultaneously optimized. Comparisons between the calculated and experimentally measured diffusion coefficients are made, where good agreement is evident. In addition, the obtained mobility parameters can reproduce a reasonable concentration profile for the Nb/Zr diffusion couple annealed at 1868 K for 5400 s. [Copyright &y& Elsevier]

Abstract As a contribution to establish a general Ni-based mobility database, the atomic mobilities in fcc Ni-Cu-Ti alloys were explored in this work. Diffusion couples were annealed at 1273 K for 150 h, and the interdiffusion coefficients were evaluated at common composition points of diffusion profiles. By combining such interdiffusion coefficients and the available thermodynamic information, the atomic mobilities of Ni, Cu and Ti in fcc Ni-Cu-Ti alloys were assessed as functions of temperature and compositions within the CALPHAD framework. Further verification of the obtained atomic mobilities was conducted by comparing the calculated and measured interdiffusvities, diffusion profiles in diffusion couples and diffusion paths in the Gibbs triangle. Highlights • Atomic mobilities of fcc Ni-Cu-Ti phases were determined. • Experimental interdiffusivities were critically evaluated. • Main and cross interdiffusivities show their peculiarities. • The profiles reveal kinetic importance for alloy microstructures. [ABSTRACT FROM AUTHOR]

Abstract: Wei et al. applied the B2-ordering model in CALPHAD to optimize the mobility parameters for the B2-bcc phase in the Ni–Al binary system from experimentally obtained diffusivities. Because the A2-bcc phase is metastable and does not exist in the phase diagram, the obtainment of its mobilities presents a challenge in the optimization process. It is pointed out that the mobilities given by Wei et al. for the disordered A2-bcc phase are not physically realistic. In addition, the simulation result for a diffusion couple is open to question according to the local equilibrium assumption. [Copyright &y& Elsevier]