In situ study of the initiation of hydrogen bubbles at the aluminium metal/oxide interface

• Published in: Nature materials 2015-09, Vol.14 (9), p.899-903
• Main Authors: Xie, De-Gang, Wang, Zhang-Jie, Sun, Jun, Li, Ju, Ma, Evan, Shan, Zhi-Wei
• Format: Article
• Language: English
• Subjects: 639/301/1023/1026; Aluminium; Aluminum; Biomaterials; Blistering; Bubbles; Condensed Matter Physics; Holes; Hydrogen; letter; Materials Science; Metals; Nanostructure; Nanotechnology; Optical and Electronic Materials; Oxides; Studies; Substrates
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4336

Gas-filled bubbles at the interface between a metal substrate and an oxide coating can cause blistering and eventual cracking of the oxide layer. The microscale mechanisms of how hydrogen bubbles form and grow have now been elucidated. The presence of excess hydrogen at the interface between a metal substrate and a protective oxide can cause blistering 1 , 2 , 3 and spallation of the scale 4 , 5 , 6 , 7 , 8 . However, it remains unclear how nanoscale bubbles manage to reach the critical size in the first place. Here, we perform in situ environmental transmission electron microscopy experiments of the aluminium metal/oxide interface under hydrogen exposure. It is found that once the interface is weakened by hydrogen segregation, surface diffusion of Al atoms initiates the formation of faceted cavities on the metal side, driven by Wulff reconstruction. The morphology and growth rate of these cavities are highly sensitive to the crystallographic orientation of the aluminium substrate. Once the cavities grow to a critical size, the internal gas pressure can become great enough to blister the oxide layer. Our findings have implications for understanding hydrogen damage of interfaces.