Growth behavior and orientation relationships in AISI 304 stainless steel during directional solidification

The formation mechanism of lathy ferrite in AISI 304 stainless steel during directional solidification was discussed in terms of the orientation relationship between ferrite and austenite. Experimental results show that most of the ferrite laths are arranged parallel and a few ferrite laths with perpendicular morphology can also be observed in the solidified microstructure. Selected-area diffraction patterns by transmission electron microscopy (TEM) and pole figures by electron backscatter diffraction (EBSD) show that Nishiyama-Wassermann orientation relationship between the lathy ferrite and austenite exists in the solidified microstructure. Based on the pole figures of the ferrite, it was found that (103) and [001] of the lathy ferrite are parallel to the sample surface and heat flow direction, respectively, during directional solidification. The elongated directions of the lathy ferrite are found to be [001], [011], and [123], which means that the lathy ferrite grows without preferential direction during directional solidification.