Hot-Dip Galvannealed Coatings Microstructure: Orientation Relationship Between ζ(FeZn₁₃) and α(Ferrite)

This study clarifies the microstructure orientation relationship in hot-dip galvannealed coating layers. The orientation relationship between ζ(FeZn₁₃) and α(ferrite) is discussed. Several galvannealed Mn–Si transformation-induced plasticity steel samples with various galvannealing times were characterized using X-ray diffraction to examine the coating layer formation. The coating layer microstructure was analyzed using transmission electron microscopy (TEM) to obtain the ζ(FeZn₁₃) and α(ferrite) orientation. According to the TEM results, we conclude that: (1) nine kinds of orientation relationships were obtained between ζ(FeZn₁₃) and α(ferrite). The misfit dislocation in the (111)_α/(111)_ζ and (111)_α/(1−11)_ζ interface is smaller than that in the other directions. (2) <110> a twin structure was observed in the (001), (112), and (111) planes in the ζ(FeZn₁₃) phase in coating layer. (3) The orientations between (011)_α//(15−2)_ζ were observed in the α(ferrite) and galvannealed coating layer interface. The results report that all (15−2)_ζ in the planes of {011}_α develop in {011}_α <112>  direction.