Invited Lecture
Diffusivity and atomic mobility in alloys

Knowledge of diffusivity is a prerequisite for understanding many scientific and technological disciplines. Accurate diffusivities and atomic mobilities in liquid and solid phases are of critical importance in quantitative description of various materials processes, such as solidification, heat treatment, recrystallization, and so on. In this talk, firstly major experimental and theoretical methods, which are employed to determine various diffusivity data in liquid and solid phases, are briefly reviewed. Focus is laid on the recently developed numerical inverse method for evaluation of interdiffusivities in solid phases, as well as the modified Sutherland equation for diffusivities in liquid phase. Secondly, the concept of atomic mobility and the most successful simulation tool, DIffusion-Controlled TRAnsformation (DICTRA) are introduced. Diffusion models recently developed for the order-disorder transition and stoichiometric compound are also briefly depicted. After that, the newly established diffusivity databases for liquid and solid phases in different alloys, including Al-, Ni-, solder and high entropy alloys, are presented. The integration of various computational techniques and experimental methods is highlighted. A few case studies in binary, ternary and even higher-order systems are demonstrated. Moreover, the reliability of the diffusivity databases is validated by comparing various calculated/model-predicted diffusion phenomena and the experimental data. Finally, the established diffusivity databases along with thermodynamic and other thermo-physical properties are utilized to realize the quantitative descriptions of microstructural evolution during solidification, and solid state transformation process in different alloys, from which the novel alloy design can be accelerated.

The financial support from the National Natural Science Foundation of China (Grant No. 51474239) and the National Key Research and Development Program of China (Grant No. 2016YFB0301101) is acknowledged.