Characterizing the Structure Evolution of Tertiary Scale during Simulated Coiling by EBSD

An oxide scale formed at 900 °C for 60 s in dry air was subjected to the simulated coiling processed with different coiling temperatures. The phase transformation behavior, especially the orientation distribution of the oxide scale, was analyzed using electron backscattered diffraction (EBSD) technique. When cooling from the coiling temperature of 650 °C, the scale consists of Fe3O4 layer, FeO layer and Fe3O4 scam. The Fe3O4 precipitates are observed in the FeO grains of the scale formed with the coiling temperature of 550 and 450 °C. With the coiling temperature of 350 °C, the decomposition of FeO is suppressed due to the low temperature. The Fe3O4 grains, which are decomposed from FeO, has the same orientation as the parent FeO grains. Moreover, the FeO grains, of which the growth direction is parallel to <001>, is easier to decompose into Fe3O4 than the grains with other orientations.