FORMATION AND GROWTH KINETICS OF INTERMEDIATE PHASES IN Fe-Zn DIFFUSION COUPLES.

Abstract

Iron/electrodeposited zinc diffusion couples were annealed at temperatures from 240 to 410 degree C. In the diffusion zone, intermediate phases appear in the order, zeta , delta //1 and GAMMA . Kirkendall markers exist always at the interface between the zeta 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 delta //1 layers and the thin double layer between the compact delta //1 and iron phases were observed in the same manner as in hot dip galvanizing. It appears that the existence of the thin double layer causes the formation of compact delta //1. For the zeta phase layer, the growth rate was decreased by the formation of the delta //1 layer and by the subsequent rapid growth of the delta //1 which occurred twice. Based on the results of this experiment growth kinetics of the intermediate phases in hot dip galvanizing are discussed.