Morphology and Crystallography of Widmanstätten Proeutectoid Ferrite

The morphologies and precipitate/matrix orientation relationships of Widmanstätten proeutectoid ferrite precipitates within large-grained samples of an Fe–0·47%C alloy, isothermally transformed above the eutectoid temperature, have been investigated using the Kossel X-ray microdiffraction technique in conjunction w th two-surface metallographic analysis. The Widmanstätten precipitates in the samples studied often have somewhat irregular overall shapes but nevertheless they usually can be described as having habit planes within 0–5° of {111} austenite planes. Individual precipitates have been observed to contain a substructure of lowangle boundaries, the misorientations between the sub-units within a precipitate being generally < 1°. In addition, it has been shown that the precipitate/matrix orientation relationship is not unique, but rather exhibits a range of relationships between the standard Kurdjumov–Sachs and Nishiyama–Wasserman fcc–bcc orientation relationships.