Atomic mobilities and diffusivities in Al alloys

Abstract

Knowledge of diffusivity is a prerequisite for understanding many scientific and technological disciplines. In this paper, firstly major experimental methods, which are employed to provide various diffusivity data, are briefly described. Secondly, the fundamentals of various computational methods, including first-principles method, embedded atomic method/molecular dynamic simulation, semi-empirical approaches, and phenomenological DICTRA technique, are demonstrated. Diffusion models recently developed for order/disorder transitions and stoichiometric compounds are also briefly depicted. Thirdly, a newly established diffusivity database for liquid, fcc_A1, L1 2 , bcc_A2, bcc_B2, and intermetallic phases in the multicomponent Al alloys is presented via a few case studies in binary, ternary and quaternary systems. And the integration of various computational techniques and experimental methods is highlighted. The reliability of this diffusivity database is validated by comparing the calculated and measured concentration profiles, diffusion paths, and Kirkendall shifts in various binary, ternary and quaternary diffusion couples. Next, the established diffusivity databases along with thermodynamic and other thermo-physical properties are utilized to simulate the microstructural evolution for Al alloys during solidification, interdiffusion and precipitation. A special discussion is presented on the phase-field simulation of interdiffusion microstructures in a series of Ni-Al diffusion couples composed of γ, γ', and β phases under the effects of both coherent strain and external compressive force. Future orientations in the establishment of next generation of diffusivity database are finally addressed.

In-situ X-ray monitoring of solidification and related processes of metal alloys

“…Self-, tracer- and chemical diffusion processes are important to understand mass transport in materials. A recent overview published by Du et al describes the different experimental techniques and different types of diffusion for aluminium alloys 41 . In particular, for self-diffusion measurements using capillary techniques and isotopes it was shown that ground-based experiments are severely affected by buoyancy effects and that microgravity experiments are able to provide buoyancy-free conditions 42 , 43 .…”

Effect of Diffusivity on the Pseudospinodal Decomposition of the γ′ Phase in a Ni-Al Alloy

“…[16,17] The simulated morphology and coarsening of precipitation in Ni-Al alloys agrees well with experimental results. [18][19][20] The purpose of this paper is to better understand the effect of diffusivity on the c¢ phase microstructure, growth and coarsening kinetics, composition difference of Al in the c matrix, width of the c/c¢ interface and the mechanism of PSD using the diffuse-interface phase field model. To focus on the variable diffusion coefficient, strain induced by lattice mismatch was ignored.…”

Revisiting the phenomenological model for effect of chemical ordering on diffusion

“…Up to now, several atomic mobility databases for disordered alloys and alloys with magnetic ordering have been developed for different multicomponent alloys, e.g. Fe-, Ni-and Al-based alloys [11,12].…”