The Effects of Temperature and Time on the Kinetic of the Intermetallic Layers Growth During Aluminizing Process of a Low Carbon Steel

Abstract

In this study, the effects of molten Al temperature and immersion time of steel samples on the joining of Al and steel and the formation and growth of intermetallic compounds, at the interface, were examined. Following surface pretreatment, steel rods were immersed into the pure aluminum melt (in an Alumina crucible) at temperatures of 680, 720, 760 and 800 Celsius and kept for different times of 5, 10, 15 and 20 minutes, at each temperature followed by air cooling after being taken out of the melt. (Then were taken out and cooled in airwhere.) Afterwards, the microstructure of interface between steel substrate and aluminium was examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Vickers hardness tests. The results showed that the main (two) intermetallic compounds formed at the Al/steel interface are FeAl3 and Fe2Al5 (were observed in reaction interface of steel substrate and aluminium. These intermetallic compounds were FeAl3 and Fe2Al5.) with a larger part of the intermetallic layer being the Fe2Al5 layer with a tongue- like morphology. As the temperature and time of immersion increase, only the thickness of the intermetallics changed without changing their composition. Thus, with increasing melt temperature and immersion time, the thickness of the intermetallic layer, especially Fe2Al5 layer, increased to a maximum value and then reduction of the thickness of the intermetallic layer was observed with further increase in temperature and time.