溶融 Zn-5mass%Al 合金浴におけるζ・Fe-Zn 相の Al-Fe 金属間化合物への変化過程

概要

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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℃. ζ・Fe-Zn phase changed to particle products mainly consisted of Zn-containing Al_5Fe_2 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⟶Al_5Fe_2+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 Al_5Fe_2 were formed in this amorphous phase. It is considered that Zn concentration at an area of the amorphous phase surrounded Al_5Fe_2 is increased with the growth of Al_5Fe_2. As a result, the area surrounded Al_5Fe_2 becomes a liquid state and Al_5Fe_2 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 (15∿60at%), Fe (10∿25at%) and Zn (15∿75at%).
社団法人日本鉄鋼協会の論文
1998-09-01