Formation of aluminide coatings by low-temperature heat treatment of Al coating electrodeposited from ionic liquid

In this study, we proposed a two-step approach to prepare aluminide coatings, namely electrodepositing Al from AlCl₃-1-ethyl-3-methyl-imidazolium chloride (AlCl₃-EMIC) ionic liquid at room temperature and subsequent heat treatment at low temperature. The adherence of the coating was checked by a simple mechanical scratch test. The surface and cross-sectional morphologies, phase structures and chemical compositions of the coatings after heat treatment were characterized by scanning electronic microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX), respectively. The deposited Al coatings were in homogenous and controllable thickness with excellent adherence to the substrate. The coatings were brittle Fe₂Al₅ and FeAl₃ phase after 5 min heat treatment at 670 °C, which transformed into ductile FeAl phase after 16 h heat treatment. The advantages of this method in eliminating the brittle Fe₂Al₅, cracks and pores in the aluminide coatings were discussed.