1998 Volume 84 Issue 9 Pages 632-636
As a purpose to investigate the changing process from Fe-Zn intermetallic compounds (IMCs) to Al-Fe IMCs in a molten Zn-5mass%Al alloy, this study has been carried out by immersing the galvanized steel sheet with Γ. Γ'. δ and ζ Fe-Zn phases as a coating layer in a Zn-5mass%Al bath at 450°C.
ζ·Fe-Zn phase changed to particle products mainly consisted of Zn-containing Al5Fe2 and the melt with less Al concentration than the Zn-5mass%Al bath at an extremely high rate. This change was found to be occurred under the two steps reaction; (1) ζ·Fe-Zn+Al(L)→ Al-Fe-Zn amorphous phase + Zn (L), (2) Al-Fe-Zn amorphous phase →Al5Fe2 + Zn(L). At the first step, the Al-Fe-Zn amorphous phase was formed around the grain boundaries of ζ·Fe-Zn phase in contact with the Zn-5mass%Al melt and then nuclei of Al5Fe2 were formed in this amorphous phase. It is considered that Zn concentration at an area of the amorphous phase surrounded Al5Fe2 is increased with the growth of Al5Fe2. As a result, the area surrounded Al5Fe2 becomes a liquid state and Al5Fe2 changed from ζ·Fe-Zn phase exists as a particle in the Zn-rich melt. The Al-Fe-Zn amorphous phase is considered to be a quasi-equilibrium phase which has a wide range of concentration for Al (1560 at%), Fe (1025 at%) and Zn (1575 at%).
