Precipitation Effects on Thermopower of a Commercial Cu–2 wt% Be Alloy

The relative and absolute thermoelectrical power (TEP) as well as the electrical resistivity of nearly fifty aged samples are determined between 5 and 290 K. The ageing is performed at 325, 280, 250, and 230 °C. While the contributions to TEP of beryllium depletion, GP zones, and phase boundaries of γ'-particles are clearly positive, that of the commercial impurities (Co, Fe) is negative being a clear function of ageing time, too. From this behaviour can be concluded that Co (and Fe) precipitates partially with Be. At temperatures T ≦ 40 K TEP indicates mainly the solute depletion in the matrix, whereas at T ≧ 60 K the contribution of the coherent interfaces begins to dominate. In the coarsening region TEP and resistivity obey approximately the Nordheim-Gorter rule (T ≧ 200 K).