SPINODAL DECOMPOSITION IN Fe-Cr ALLOYS: EXPERIMENTAL STUDY AT THE ATOMIC LEVEL AND COMPARISON WITH COMPUTER MODELS—Ⅲ. DEVELOPMENT OF MORPHOLOGY

摘要

The fine-scale three-dimensional microstructures formed during spinodal decomposition in Fe-Cr alloys are characterized using two novel methods. In the first, a fractal analysis is used to characterize the interface between the phases and, in the second, the interconnectivity of the structure is determined from topology. It is found that the interface between Fe-rich α and Cr-enriched α′ regions in the experimental data and Monte Carlo simulations exhibit fractal behaviour whereas the microstructures from the solution to the Cahn-Hilliard-Cook model do not. Topological methods are used to characterize the complex α′ microstructures in terms of the number of cavities and loops. The decrease in the number of large scale loops in the microstructure, during thermal ageing, is shown to correlate with the increasing microstructural scale. The number of small scale loops is found to correlate with the complexity of the interface between the α and α′ regions.