Formation and Growth Kinetics of Intermediate Phases in Fe–Zn Diffusion Couples

Abstract

The iron-electrodeposited zinc diffusion couples were annealed at temperatures from 240 to 410°C. In the diffusion zone, intermediate phases appear in the order of ζ, δ1, and Γ phases. Kirkendall markers exist always at the interface between the ζ and zinc phases. This pronounced Kirkendall effect means that there is a one-sided diffusion of zinc atoms by a vacancy mechanism.The compact and palisade δ1 layers and the thin double layer between the compact δ1 and iron phases were observed in the same manner as in the case of hot dip galvanizing. It appears that the existence of the thin double layer causes the formation of the compact δ1. For the ζ phase layer, the growth rate was decreased by the formation of the δ1 layer and by the subsequent rapid growth of the δ1 which occurred twice. From the results of this experiment growth kinetics of the intermediate phases in hot dip galvanizing were discussed.