Microstructure and Thickness of 55 pct Al-Zn-1.6 pct Si-0.2 pct RE Hot-Dip Coatings: Experiment, Thermodynamic, and First-Principles Study.

The microstructure and thickness of 55 pct A1-Zn-1.6 pct Si-0.2 pct RE coatings during continuous hot-dip on Q235 steel were investigated in this work. The experimental results revealed that the intermetallic layer was composed of the FeAl, FeAl, and α-FeAlSi phases. The results of thermodynamic calculations with Pandat software package (CompuTherm, LLC, Madison, WI) indicated that FeAl and α( β)-FeAlSi phase precipitated during the period of temperature cooling, which was consistent with experimental result. Then, the thickness of intermetallic layer was characterized. It was shown that the thickness of intermetallic layer decreased after 0.2 wt pct RE was added. Finally, a first-principles calculation was performed to interpret the effect mechanism of RE on the thickness of intermetallic layer. The results indicated that La substitution in FeAl and FeAl phases could grab electronic charges from Al atoms and weaken the formation of Fe-Al compounds. [ABSTRACT FROM AUTHOR]