THE OXIDATION PROCESS IN THE TEXTURED THIN TAPES OF BINARY COPPER-BASED ALLOYS

In the present work, the authors studied the development of the oxidation process in some binary copper alloys (Cu - 40 % Ni, Cu - 30 % Ni, Cu - 1.6 % Fe, Cu - 0.4 % Cr). The authors determined the principal locations for the formation of corrosion centers on the surface of textured tape substrates of Cu-Me alloys (where Me=Ni, Cr, Fe) after annealing in an oxidizing atmosphere for 5, 30, and 250 min at the temperature of 700 °С. The study established that the oxidation of the surface of thin tapes of Cu - 0.4 % Cr and Cu - 1.6 % Fe alloys is not homogeneous, in contrast to the Cu - 40 % Ni and Cu - 30 % Ni alloys. The corrosion centers formed more intensively on the segregated particles of the alloying element - pure chromium or iron with a bcc lattice. The study discovered that the oxide film formed as a result of prolonged annealing, in Cu-Cr and Cu-Fe alloys, has a greater thickness in the zone of grain boundaries. According to the X-ray spectrum analysis, in the spectra taken from the boundaries, the higher oxygen content is registered than in the central zone of a grain. The study shows that in the textured tapes of Cu-Cr and Cu-Fe alloys, both the surface oxidation and internal oxidation of tapes occur in the process of short-term annealing (700 °С, 5 and 30 min). As a result of electron-diffraction analysis, the authors identified that, in the course of oxidation, a layer of complex spinel-type CuMe₂O₄ (Me=Cr, Fe) oxide appears on the alloying element particles during the annealing, and the dispersed copper oxides, mainly Cu₂O with a small quantity of CuO, are produced in the copper matrix.

textured tapes, binary copper alloys, oxidation, surface structure, complex oxides