Dependence of texture development on the grain size of tertiary oxide scales formed on a microalloyed steel

Both orientational and geometrical characteristics of grains in tertiary oxide scales have been quantitatively investigated using the electron backscatter diffraction (EBSD) technique. Phase and orientation mappings demonstrate that the {001} planes of magnetite and the {0001} planes of hematite are parallel to the direction of oxide growth. Pole figures (PFs) as scattering plots clearly display the direct correlation between the orientations and microstructure sites of magnetite grains. Magnetite grains develop a strong rotated cube texture component that shifts to the {100}< 210 > component, whereas those with the grain size of 1-5 μm develop the {001}< 100 > cube texture component. The refined magnetite grains surrounding the abnormal ones can be a combined process, including magnetite pro-eutectoid during hot rolling and cooling and re-oxidation during air-cooling. Our findings offer insights toward further understanding of the link between the geometrical and orientation parameters of grains with respect to the deformation behaviour of oxide scales formed at elevated temperatures.