Abstract
Fe specimens were annealed in molten Bi containing 1-20 mass%Zn at 553 to 673 K, in order to investigate the structures of Fe-Zn alloy layers formed by reactive diffusion between Fe and molten Bi-Zn. On surfaces of the specimens, seven kinds of alloy layers composed of the following Fe-Zn intermetallic phases were formed depending on the annealing condition: (1) Γ, (2) Γ and Γ1, (3) Γ, Γ1 and δ1, (4) Γ, Γ1, δ1 and ζ, (5) Γ, δ1 and ζ, (6) δ1 and ζ, and (7) ζ. The structure of the alloy layer changed in order of (1)→(2)→(3)→(4), (1)→(2)→(3)→(5) or (1)→(3)→(7) with increasing Zn content of molten Bi and in order of (7)→(6)→(5)→(4) with annealing time in molten Bi saturated with Zn. It seems that the Fe-Zn intermetallic phase having zinc activity approximately equal to that of molten Bi-Zn is formed at an outer surface of the alloy layer and that the lag in the appearance of δ1, Γ and Γ1 phase layers in the molten Bi saturated with Zn is caused by the formation of ζ phase layer having a non-equilibrium composition ranging from the δ1 to ζ phases.
