Internal friction study of environmental effects on metals and alloys

The internal friction method was applied for studying structural changes occurring in bulk metal due to its interaction with the environment. It was shown that the active dissolution of metal or its oxidation is accompanied by the generation of non-equilibrium vacancies. Diffusive transfer of vacancies into the bulk causes considerable rearrangements of the defect structure of the crystal and, therefore, changes in its anelastic response. Environmental effects have been studied in pure copper subjected to oxidation in a 0.3 N solution of NaNO₂. Such an interaction resulted in the formation of Hasiguti peaks. A similar effect was found in admiralty brass after oxidation in hot tap water, resulting in selective dissolution of zinc. Low-temperature internal friction peaks were also found in the range 150–200 K in Al–5 Mg industrial alloy subjected to active dissolution in 0.05 N KOH solution. The results obtained are discussed in terms of the applicability of the internal friction method for predicting the susceptibility of metals and alloys to environmentally assisted cracking.