Mechanical Stability of Passivation Films Deposited on Aluminium Substrates

The damage of films of two different passivation materials deposited on aluminium substrates was investigated. These systems were subjected to uniaxial stretch in an in situ tensile testing device adapted to a scanning electron microscope. Successive stages of crack development were observed: the failure is first in the film, then at the interface. The presence of a thermally grown aluminium oxide interlayer delays the decohesion process. The substrate surface roughness weakens the systems. The evolution of the crack density with the longitudinal strain was analysed and then fitted with a model based on a Weibull distribution function.