THE DECOMPOSITION KINETICS OF CU-1 AT.PERCENT-CO AT 823 K, STUDIED BY BRIGHT-FIELD ZONE-AXIS-INCIDENCE TRANSMISSION ELECTRON-MICROSCOPY

The homogeneous decomposition of a Co-1 at.% Co alloy at 823 K has been investigated by bright-field-zone-axis-incidence transmission electron microscopy. The new method allows detection of Co precipitates with radii r greater than or equal to 1 nm, independent of their position in the foil, and the contrast of the particles is straightforwardly related to their real dimension. So we were able to measure the particle density N-v, the mean radius (r) over bar, the distribution function f(r) of the radii and the pair correlation function PCF (R) of the particle spacings R with high accuracy. The data have been compared with the predictions of a modified Langer-Schwartz theory. Best correspondence is obtained with a value of 240 mJ m(-2) for the interfacial energy per unit area of Cu-Co. The spacings R of the particles showed no significant regularity as expected from an initial spinodal-like precursor fluctuation of the Co concentration.