The nature of the periodic microstructure in Fe–Ti alloys

The morphology of the periodic microstructure and its influence on the process of Fe–Ti alloy decomposition were investigated by means of transmission electron microscopy, field-ion microscopy and X-ray diffraction. The tweed structure is a system of long cylindrical columns enriched in titanium and situated along the elastically soft directions of the Ti-depleted Fe-matrix. The tweed structure forms in the monophase region of the phase diagram as a result of the tendency of Fe–Ti alloys to separation and dissolves during aging before the precipitation of a new Fe2Ti phase.