Alloying Behavior of Electrogalvanized Steel Sheet by Heating

Abstract

Alloying behavior of electrogalvanized coatings on a steel sheet was studied mainly by the method of X-ray diffraction at temperatures especially from 240 to 340°C. At the temperatures below 300°C, a cubic intermetallic phase like Γ is observed besides ζ phase from the beginning of the reaction. This Γ-like phase is electrochemically similar to ζ phase, and its {111} planes are predominantly oriented parallel to the original steel/zinc interface. Then another cubic phase is formed between steel and Γ-like phase after latent time more than a couple of hours. This secondary cubic phase is nobler than the first one. Within a range of 320 to 340°C, Γ-like phase preferentially oriented is formed and grown up. Then this phase is transformed into δ₁ phase. At temperatures above 380°C, Γ-like phase preferentially oriented is not observed, and cubic phases are not formed at the beginning of the reaction, and ζ and δ₁ phases are grown up since the beginning of the reaction. At these temperatures, cubic intermetallic phases, which are formed late, are not preferentially oriented.