The morphology and substructure of {225}F martensite in an Fe−Mn−Cr−C alloy

A transmission electron microscopy and diffraction study of martensite plates in an Fe-3 pct Mn-3 pct Cr-1 pct C alloy was carried out with particular attention to details of the martensite substructure. A corresponding optical metallographic study of plate morphology was made. A variability in martensite substructure was observed from plate to plate, although a (252)_F ^* plate was generally associated with (112)_B transformation twins and {111}_F stacking faults. The particular (111)_F fault variant gave rise to a wedge-shaped plate morphology. Planar {101}_B inhomogeneities were frequently observed in the martensite, and most of these appear to be derived from austenite stacking faults. In general, more than one type of inhomogeneity was observed in a single martensite plate and the “typical” plate substructure was rather difficult to characterize, although the habit plane was found invariably to be (252)_F.