Abstract
The high-resolution lattice imaging technique of transmission electron microscopy has been utilized to monitor the decomposition process in Au–Ni spinodal alloys. Individual measurements were made of lattice fringe spacings which are sensitive to composition variations at the atomic plane level. The results indicate that rather smooth and regular composition waves are obtained at an early state of decomposition, and that later stage coarsening results in larger amplitude fluctuations. This provides direct evidence of simultaneous decomposition and coarsening which agrees with theoretical predictions.
An analysis of reaction kinetics and morphology suggests that the decomposition is one-dimensional, even after very long aging times. This behavior is believed to be the combined result of a large matrix strain energy associated with the decomposition product and the slow decomposition kinetics due to low temperature aging (at 423 K).
