Observations on the morphology and crystallography of proeutectoid ferrite

Abstract

Proeutectoid ferrite precipitates in Fe-0.47% C austenite partially transformed at 730°C have been studied using Kossel X-ray diffraction and detailed two-surface serial sectioning. Previous observations of habit planes near {111} in this system have been confirmed. However, there are many morphological irregularities and a minority of precipitates possess major interfaces which clearly deviate from {111} by 10–15°, which from measurements of the orientation relationship and maximum growth direction appear essentially to be of the approximate {223} type observed recently. The results are compared with various previous studies and it is concluded that the near {111} habit is not simply a pseudo-habit-plane characteristic only of longer reaction times and furthermore may only occur when a precipitate is formed under conditions of low supersaturation.