Iron–Zinc Alloying Reaction on Interstitial Free Steels

Publisher Website
Google Scholar
Abstract
Effects of the processing conditions on the coating microstructure of galvannealed steel sheets have been investigated with special reference to the Fe–Zn alloying reaction on an interstitial free steel substrate. The results showed that the Fe–Zn alloying reaction could be classified into three processes: suppression of Fe–Zn alloying reaction by Fe–Al intermetallic compound, formation of ζ-phase, and rapid growth of outburst structure (mainly composed of δ1-phase). The formation of ζ-phase was closely correlated with alloying temperature, and was explained in terms of Zn–Fe equilibrium phase diagram. The relationships between properties and coating microstructure were also investigated. An increase in the amount of ζ-phase increases the frictional coefficient while enhancing the antipowdering property of the coating. However, the frictional properties of the galvannealed layer could be improved by electroplating with an Fe rich Fe–Zn alloy layer of more than 2 g m-2.