Heteroepitaxial growth of Fe2Al5 inhibition layer in hot-dip galvanizing of an interstitial-free steel

This work presents characterization results on inhibition layers formed on a TiNb-stabilized interstitial-free steel after short time galvanizing. The Fe-Al and steel interface was free from oxide, so that the Fe-Al intermetallic compound could directly nucleate on ferrite grains. Electron diffraction performed in a transmission electron microscope showed that only Fe2Al5 was formed and it had a well-defined orientation relationship of [110]Fe(sub/2)Al(sub/5)// [111]Fe, (001)Fe(sub/2)Al(sub/5)//(011)Fe and (110)Fe(sub/2)Al(sub/5)//(211)Fe with Fe substrate. The structure of the interfaces between Fe2Al5 and Fe is discussed. The epitaxially nucleated Fe2Al5 grains on Fe substrate had very small grain size, 20 nm or less, and several variants were intimately mixed. The grains grew rapidly to hundreds of nanometers toward the Zn side.