Formation of hydrogen blisters during the solution treatment for aluminum alloys

Abstract

The solution treatment of aluminum alloys can be restricted by the presence of porosity defects caused by the moisture present in the process or by the hydrated front on the material surface. Hydrogen blisters cause deleterious effects on mechanical properties and surface finish. However, the formation of bubbles in solid aluminum is not caused only by the known reaction 2Al+3H2 O=3H2 +Al2 O3 , as it does not explain the interaction of the aluminum oxide layer with the formation mechanisms. In addition, the literature approaches show that there is more than one mechanism for the formation of these defects, but no work has made an association between them. Thus, the objective of this work is to carry out extensive research on the state of the art of hydrogen blister formation in aluminum alloys during the solubilization heat treatment. Contemplating different proposed mechanisms of bubble formation on the surface and structure, the analysis of this association of approaches indicated that the mechanisms depend on both permeability, where the hydrated oxide front creates passage for the formation of blister in the sublayer, as well as diffusion and hydrogen solubility in the microstructure.