1998 Volume 84 Issue 9 Pages 637-642
Following the previous report, it has been investigated the changing process from Fe-Zn intermetallic compounds (IMCs) to Al-Fe IMCs in a molten Zn-5mass%Al alloy at 450°C.
Γ·Fe-Zn phase changed directly to Zn-containing Al5Fe2 at an extremely high rate.Γ phase had a strong orientation of {110} plane parallel to the steel surface, but Zn-containing Al5Fe2 had not a significant orientation. And a special orientation relationship between Γ phase and Al5Fe2 could not be found. Combining these results with the previous results on the changing process from ζ·Fe-Zn phase (two steps reaction; ζ·Fe-Zn phase→Al-Fe-Zn amorphous phase→Al5Fe2), it is considered that whether Fe-Zn IMCs change to Al5Fe2 by the direct reaction or the two steps reaction depends on the Fe atomic concentration of these IMCs. After the whole of Γ·Fe-Zn layer changed to Zn-containing Al5Fe2, Al5Fe2 layer peeled off the steel substrate. This is considered to be due to that a Zn-rich phase which had been formed like a chain in Zn-containing Al5Fe2 layer changed to voids by the outer diffusion of Zn in this phase. The Zn-rich phase is understood to be formed by the concentration of Zn discharged from Γ·Fe-Zn phase during changing to Zn-containing Al5Fe2.
