Selective alloying of pure aluminum with varying amounts of magnesium using friction stir processing for improved mechanical and corrosion-resistant properties

This study investigates the effects of adding different amounts of Mg to the surface of pure Al substrate using friction stir processing (FSP) technique to prepare Al-Mg solid solutions. For this purpose, machined grooves on the surface of the pure Al plates were filled by bulk Mg blocks and FSPed to form Al-Mg solid solution layers with-2.0, 4.5, and 33.9 at.% Mg. The chemical composition, microstructure, and surface Volta potential of the surface alloyed layers were studied by SEM/EDS, XRD, and SKPFM, respectively. The results revealed that incorporating Mg into the Al substrate causes a considerable refinement of the microstructure, resulting in a significant increase in Vickers hardness number from 25 to 208.4 HV (-734% increase). As the Mg content in the alloyed layer increased, a transition from a single-phase solid solution structure to a dual-phase structure was observed. Based on the potentiodynamic polarization results, it is evident that the corrosion resistance of the single-phase alloyed layer can match that of marine-grade aluminum alloys.