Crystallography of intermetallic interface layers in hot-dip galvanizing steel sheets

The crystallography of the intermetallic phases forming at the zinc-film/substrate interfaces in hot-dip galvanizing steel sheets has been investigated mainly by means of scanning electron and cross sectional transmission electron microscopies. Zinc atoms penetrating into a ferrite lattice precipitate within the ferrite as monoclinic zeta-phase rods with parallelogram cross sections initially in contact with the interface. The growth direction of the zeta-phase rod is probably the [001](zeta) which lies parallel to a [111](alpha). The orientation relationship between zeta and the substrate ferrite, [001](zeta)//[(1) over bar 11](alpha), (100)(zeta)//(101)(alpha), (010)(zeta)//(12 (1) over bar)(alpha), can be expected by considering both the results of scanning microscopy and the atomic configurations of zeta phase and those of ferrite. The additional heat cycle up to 723 K to produce thin foils for cross sectional transmission electron microscopy after the hot-dip galvanizing process induces the formation of delta(1)-phase at the ferrite/zeta interphase boundary. No specific orientation relationship between the delta(1)-phase and the substrate ferrite was obtained.