Instability criteria for identical systems of binary alloys with ordering and phase separation are derived from linearized coupled kinetic equations for local composition and local degree of order. The analysis clearly shows that deviation from stoichiometry leads to instability against heterogeneous ordering associated with compositional fluctuations, when the degree of order is around 1/√3 of the equilibrium value. Heterogeneous ordering or spinodal decomposition is expected to occur even in the single phase field of the order phase as well as within the miscibility gap between ordered and disordered phases. Transmission electron microscopy on an Fe-14.6 at.% Si alloy revealed that D03-type ordering is accompanied by heterogeneous fluctuations of the degree of order as predicted by the derived instability criteria.
|Number of pages
|Zeitschrift fuer Metallkunde/Materials Research and Advanced Techniques
|Published - Dec 1998
All Science Journal Classification (ASJC) codes
- Metals and Alloys