THE VARIANTS OF THE ORIENTATION RELATIONSHIP BETWEEN AUSTENITE AND CEMENTITE IN FE-30WT-PERCENT-MN-1.0WT-PERCENT-C ALLOY

Abstract

The morphology in cementite precipitation and the orientation relationship between cementite plates and austenite matrix on aging of Fe-30wt%Mn-1.0wt%C alloy have been investigated by transmission electron and optical microscopies. On aging at 550-degrees-C, Widmanstatten-like cementite plates having the Pitsch orientation relationship (OR) were precipitated within the austenite matrix. But on aging at 700-degrees-C, colonies composed of cellular cementite and austenite plates were dominantly precipitated and grew out of grain boundaries. The latter cementite plates also preserved the Pitsch OR with the austenite counterparts. From the consideration of atomic habit plane relationships we deduced 4 different variants of the Pitsch OR. Only two pf them could be identified from the transmission electron microscope (TEM) selected area diffraction (SAD) patterns. In the optical micrographs, all four variants respectively with their own easy growth direction of the cementite plates were distinguished.