Effect of exfoliated few-layered graphene on corrosion and mechanical behaviour of the graphitized Al–SiC surface composite fabricated by FSP

The influence of friction stir processing parameters and the subsequent evolution of microstructures and corrosion behaviour of Al–SiC surface composites fabricated in the presence of graphitic flakes are presented in this paper. The circumferential shear stress exerted by the rotating tool exfoliates the graphite flakes into few-layered graphene during processing. These graphene flakes preferentially occupy both the grain boundaries and the SiC–Al interface during recrystallization. The potentiodynamic polarization test, in 3.5 wt% sodium chloride (NaCl) solution, is conducted for samples processed at various tool rotational speeds and it is found that the presence of this thin graphitic layer at these locations reduces the intergranular and interfacial corrosion to a great extent. The tool rotational speed has a significant influence on processing, and samples fabricated at an optimum tool rotational speed of 2200 rpm shows better corrosion resistance and mechanical properties as compared to that at lower and higher speeds. Raman spectroscopic analysis, X-ray diffraction studies and microhardness tests corroborate the experimental results and the proposed mechanisms.