Variables affecting growth and morphology of the intermetallic layer (Fe2Al5)

A steel substrate containing 0.4% carbon was hot-dip aluminized in pure Al and Al-11 wt.% Cu alloy. During the aluminizing process, an intermetallic layer (Fe2Al5) was developed at the interface between the aluminizing metal and the steel substrate. The effects on its growth and morphology resulted due to variation in compositions of aluminizing metal, carbon content of the steel substrate, aluminizing temperatures (675-950 degrees C) and dipping times (1-10 min) were investigated. In pure Al, the interrnetallic layer was thick and it showed a finger-like growth with the substrate. While in the Al-Cu alloy, it was thin enough and its growth was almost smoother. Its thinning was attributed to the formation of tetragonal intermetallic phases, Al2Cu and Al2Cu2Fe, on the surface of the aluminized steel. In both melts, its thickness increased with increasing aluminizing temperatures in the range 675-775 degrees C, while above this range it was found constant. Likewise, it increased rapidly with the increase of the dipping time up to 4 min, after that with increasing time it increased very slowly. Conversely, the variations in both the aluminizing temperature and the dipping time did not influence morphology of the intermetallic layer. (C) 2011 Elsevier Inc. All rights reserved.