SPINODAL DECOMPOSITION IN FE-CR ALLOYS - EXPERIMENTAL-STUDY AT THE ATOMIC-LEVEL AND COMPARISON WITH COMPUTER-MODELS .3. DEVELOPMENT OF MORPHOLOGY

The fine-scale three-dimensional microstructures formed during spinoda l decomposition in Fe-Cr alloys are characterized using two novel meth ods. In the first, a fractal analysis is used to characterize the inte rface between the phases and, in the second, the interconnectivity of the structure is determined from topology. It is found that the interf ace between Fe-rich alpha and Cr-enriched alpha' regions in the experi mental data and Monte Carlo simulations exhibit fractal behaviour wher eas the microstructures from the solution to the Cahn-Hilliard-Cook mo del do not. Topological methods are used to characterize the complex a lpha' microstructures in terms of the number of cavities and loops. Th e decrease in the number of large scale loops in the microstructure, d uring thermal ageing, is shown to correlate with the increasing micros tructural scale. The number of small scale loops is found to correlate with the complexity of the interface between the alpha and alpha' reg ions.