Atomic mobilities and diffusivities in the fcc, L1₂and B2 phases of the Ni-Al system

Abstract

A phenomenological model was utilized to describe diffusivities in the γ (fcc) /γü (L12) and A2/B2 phases of the NiüAl system. An effective strategy, which takes the homogeneity range and defect concentration into account, was developed in the present work to optimize the atomic mobilities of γü phase. Such a strategy results in a dramatic decrease in the number of atomic mobility parameters to be evaluated for the L12 phase. The measured composition- and temperature- dependent diffusivities in the NiüAl system have been well replicated by the present mobility descriptions. For the L12 phase, comprehensive comparisons show that with fewer model parameters the presently obtained mobilities yield a better fit to experimental diffusivities, compared with previous assessments. The mobility descriptions are further validated by comparing calculated and measured concentration profiles for various diffusion couples. The time-dependent Al composition profile for the annealed vapor Al / γ couple is accurately described for the first time.

Self-Diffusion Coefficient of fcc Mg: First-Principles Calculations and Semi-Empirical Predictions

“…The predicted value through these two means of methods are compared with the NIST data from Zhang et al [39] As shown in Fig. 7, the predicted self-diffusion mobility of fcc Al with LDA pseudopotential shows an excellent agreement with the mobility by Zhang et al [39] It should be noted that LDA pseudopotential has a better estimation of self-diffusion mobility of fcc Al than GGA without correction (correction for surface energy [25] ). However, the self-diffusion mobilities evaluated with the first three kinds of semi-empirical equations bear large discrepancy from the NIST data.…”

“…Subscript (a) represents the self-diffusion coefficients of fcc Al is from the NIST data. [39] Subscript (b, c) indicates the self-diffusion coefficients of fcc Al are evaluated from first-principles calculations using LDA and GGA, respectively. Subscript (d-g) represents the self-diffusion coefficients of fcc Al are predicted from the four kinds of semi-empirical equations in the present work Section I: Basic and Applied Research…”

Assessment of Atomic Mobilities in fcc Al-Ag-Zn Alloys

“…During the assessment, the self diffusivities of fcc Ag, Al and Zn and the impurity diffusivities of Zn in fcc Al assessed by Ghosh, [51] Zhang et al, [52] Cui et al [53] and Du et al [54] respectively were accepted. The atomic mobility parameters for fcc Al-Zn alloys were taken from the recent work of Cui et al [55] Thus, the atomic mobilities of the other two sub-systems, Al-Ag, Ag-Zn, together with the ternary Al-Ag-Zn system are evaluated in the present work.…”

On Sluggish Diffusion in Fcc Al–Co–Cr–Fe–Ni High-Entropy Alloys: An Experimental and Numerical Study

“…In addition, the parameters of the end-members in all sub-binary systems shown in Equation (4) are from Refs. [23][24][25][26][27][28][29][30], as listed in Table 2. These parameters are fixed during the evaluation.…”