A TEM study of the crystallography of lath-shaped austenite precipitates in a duplex stainless steel

The morphology of austenite (fcc) precipitates in a duplex stainless steel (DSS) is dominated by rods distributed in a ferrite (bcc) matrix. Minority of austenite precipitates also exhibits a lath shape, a common morphology in fcc to bcc transformations rather than a bcc to fcc transformation in a DSS. While the rod-shaped austenite precipitates in a DSS have been interpreted in previous investigations, precipitates with a lath shape were not well understood. This study focused on the lath-shaped austenite by using transmission electron microscopy. The habit plane of lath-shaped austenite was observed to be free of dislocations, but one array of dislocations was observed in the major side facet with a spacing of 9.6 nm and Burgers vector of [110] f /2|[010] b . These observations of crystallographic features were interpreted consistently by an O-line and good matching site analysis. Different morphologies in a DSS and similar morphologies in fcc to bcc and bcc to fcc transformations are compared and discussed.