The iron-zinc alloying reactions which take place during hot dip galvanizing and galvannealing processes were investigated, with special reference to the formation and growth behavior of iron-zinc intermetallic compounds.The SEM observation and X-ray diffraction analysis of the intermetallic compounds which had formed on laboratory galvanized Ti stabilized interstitial-free steel and on low carbon aluminum killed steel sheets showed that there were two types of elementary iron-zinc alloying reactions ; one was the formation ofã nd 5, crystals and another was so-called outburst reaction.Thecrystal nucleated on the Fe-AI intermetallic compound which had been formed on the steel surface, and grew into the melt as a single phase crystal. Simultaneously, the outburst structure was generated as a result of the direct reaction between iron and molten zinc, and grew as a multiple phase structure (~, 8, and r phases). The~phase was generated at the isothermal galvannealing temperature of less than 773 K, and it was explained in terms of the iron-zinc equilibrium phase diagrem (peritectic temperature ofphase). 35 (1995), No. 11 Fig, l.

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