Internal friction study of environmental effects on metals and alloys

The internal friction method was applied for studying structural changes oc curring in bulk metal due to its interaction with the environment. It was s hown that the active dissolution of metal or its oxidation is accompanied b y the generation of non-equilibrium vacancies. Diffusive transfer of vacanc ies into the bulk causes considerable rearrangements of the defect structur e of the crystal and, therefore, changes in its anelastic response. Environ mental 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 oxidati on in hot tap water, resulting in selective dissolution of zinc. Low-temper ature 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 solutio n. The results obtained are discussed in terms of the applicability of the internal friction method for predicting the susceptibility of metals and al loys to environmentally assisted cracking. (C) 2000 Elsevier Science S.A. A ll rights reserved.