The Pitsch-Petch orientation relationship in ferrous pearlite at small undercooling

The factors behind the occurrence of the Pitsch-Petch pearlitic orientation relationship (OR) in ferrous systems are investigated using a combination of crystallographic information obtained through electron-backscatter diffr action (EBSD) and knowledge of the three-dimensional (3-D) morphology of pe arlite from serial sectioning. Both hypereutectoid and hypoeutectoid ferrou s systems of various compositions providing a variety of morphologies are e xamined to consider the relationship between pearlite nucleation sites and ferrite-cementite interlamellar ORs. It is shown that the Pitsch-Petch OR o ccurs when a colony is cementite nucleated and this conclusion is valid for both sides of the eutectoid composition.