Mechanisms of phase transformations within the miscibility gap of Fe-rich Fe-Al alloys

Abstract The coherent phase diagram of the Fe-Al system possesses a tricritical point where a line of higher-order transitions ends at a miscibility gap at about 23 at.% Al and 615°C. Rules of general applicability governing phase separation within the miscibility gap of such a system are developed. Application of the rules to the Fe-Al system results in detailed predictions about the mechanisms of decomposition and ordering reactions and their sequences. Electron microscopy is used to study the reactions experimentally and the results are in agreement with theoretical predictions.

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