Atomic transport in metallic systems: mechanisms, characterization and multiscale modelling

• A hierarchical cross-scale theoretical framework for atom diffusion in metals. • Experimental approaches for diffusion phenomenon and mechanisms. • Multiscale simulations and the integration of AI-driven strategies for diffusion. With metallic materials increasingly deployed in extreme service scenarios (e.g., high temperatures, elevated stresses, and irradiation), optimizing key properties such as strength, plasticity, creep resistance, and radiation tolerance has become imperative. Atomic diffusion governs microstructural evolution (i.e., regulating dislocation motion, phase boundary migration, and solute segregation), and thus underpins both alloy performance tuning and advances in diffusion physics. This review consolidates recent progress across diffusion theory, atomistic mechanisms, experimental characterization techniques, and multiscale simulation frameworks for metallic systems. It systematically explores how atomic interactions, chemical ordering, local lattice distortions, and external fields modulate diffusion behavior, and further discusses emerging data-driven strategies in the context of their integration with experiments and modelling for the interpretation or modelling of transport behavior. By bridging atomic-scale insights with macroscopic material responses, this work provides a unified framework for understanding and engineering diffusion in metallic materials.