Gradient nanostructures (GNSs) have been optimized in recent years for desired performance.The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different 15-eg2373cl interfaces that provide fundamental understanding for advancing the traditional surface alloying processes.In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer.We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples.Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced.
Finally, the perspectives on read more current research in this field are discussed.