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

The morphology in cementite precipitation and the orientation relation ship 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 ce mentite plates having the Pitsch orientation relationship (OR) were pr ecipitated within the austenite matrix. But on aging at 700-degrees-C, colonies composed of cellular cementite and austenite plates were dom inantly precipitated and grew out of grain boundaries. The latter ceme ntite plates also preserved the Pitsch OR with the austenite counterpa rts. From the consideration of atomic habit plane relationships we ded uced 4 different variants of the Pitsch OR. Only two pf them could be identified from the transmission electron microscope (TEM) selected ar ea diffraction (SAD) patterns. In the optical micrographs, all four va riants respectively with their own easy growth direction of the cement ite plates were distinguished.