X-ray diffraction and TEM analysis of Fe–Al alloy layer in coating of new hot dip aluminised steel

Abstract

The phase structure in the Fe-Al alloy layer of a new hot dip aluminised steel has been researched by means of electron probe microanalysis, X-ray diffraction and TEM, etc. The test results indicated that the Fe-Al alloy layer of the new aluminised steel was composed of Fe₃Al, FeAl, a few Fe₂Al₅ and α-Fe (Al) solid solution. There was no brittle phase containing higher aluminium content, such as FeAl₃ (59.18 wt-%Al) and Fe₂Al₇ (62.93 wt-%Al). The tiny cracks and brittlement, formerly caused by these brittle phases in the conventional aluminium coated steel, were effectively eliminated. There was no microscopic defect (such as tiny cracks, pores or loose) in the coating. This is favourable for resisting high temperature oxidation and corrosion of the aluminised steel.