Room temperature plasticity in thermally grown sub-micron oxide scales revealed by micro-cantilever bending

We propose a new geometry for focused ion beam milled micro-cantilevers, which allows production of residual stress-free, isolated thin film specimens from film-substrate systems. This geometry was used to demonstrate the presence of permanent deformation in about 200 nm thick thermally grown oxide scales on a Ni-base superalloy, after applying large bending displacements in-situ in a scanning electron microscope. Stiffness measurements performed before and after the bending tests confirmed the absence of micro-cracks, leading to the conclusion that plastic deformation occurred in the oxide scale. The proposed method is extendable to other film-substrate systems and testing conditions, like non-ambient temperatures