Crystallography of Intermetallic Interface Layers in Hot-dip Galvanizing Steel Sheets

摘要

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 ζ-phase rods with parallelogram cross sections initially in contact with the interface. The growth direction of the ζ-phase rod is probably the [001 ]_ζ which lies parallel to a < 111 >_α. The orientation relationship between ζ and the substrate ferrite, [001]_ζ//[111]_α, (100)_ζ//(101)_α, (010)_ζ//(121)_α, can be expected by considering both the results of scanning microscopy and the atomic configurations of ζ 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 δ_1-phase at the ferrite/ζ interphase boundary. No specific orientation relationship between the δ_1-phase and the substrate ferrite was obtained.