Fig. 3. Preferential growth of wormholes in the diffusion-induced grain boundary migration (DIGM) zone.
a–c EBSD evidence showing rugged grain boundaries (GBs) after DIGM. d Evidence of salt penetration: SEM imaging shows that salt exists on the backside of the 30-μm-thick foil sample. e Representative SEM image corresponding to the boxed area in (b), which shows a rugged GB after molten salt corrosion. f Schematic drawing of the key features in (e). g STEM-HAADF image, STEM-EDX mapping, and SAED evidence for DIGM. h Schematic illustration of the DIGM process and the preferential growth of wormholes in the DIGM zone.