A Crystallographic Study of Pearlite Growth in Steels

Abstract

The crystallography of pearlite during the growth process in plain and alloy steels is investigated by transmission electron microscopy. The results show that the ferrite/cementite orientation is controlled by one of the two relations, viz., Pitsch or Bagaryatskii. The relation basically depends on the mechanism of nucleation either at “clean” austenite boundaries or on the pre-existing proeutectoid phase. The degeneration or spheroidization of cementite lamellae on reducing the transformation temperature is attributed to insufficient diffusion of carbon to maintain the lamellar shape. This process has no influence on the lattice relationship. In consistence with this conclusion, the interlamellar spacings are almost constant, despite the change in the pearlite morphology.