Microstructural evolutions and corrosion behavior of nanocomposite AlCoCrFeNi2.1 high-entropy alloy produced via friction stir processing

Having homogenized the as-cast AlCoCrFeNi2.1 high-entropy alloy followed by cold rolling and subsequent annealing, this study produces surface nanocomposite using friction stir processing (FSP). Three weight percentages of SiC nanoparticles sized between 45 and 60 nm were added during FSP. The microstructural evolutions and corrosion behavior were assessed after and before FSP. As part of the investigation, a series of potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were conducted in a 3.5 wt% NaCl solution. Through friction stir processing, the initial microstructure underwent significant modification due to dynamic recrystallization and the Zener pinning applied by SiC-reinforcing nanoparticles. The hard B2 phases, which function as preferred sites for localized corrosion, were broken and redistributed during FSP, resulting in a notable increase in corrosion resistance. After performing FSP, the cold-rolled and annealed sample exhibited a significant increase in corrosion resistance, from 1.7 kΩ.cm2 to 129.4 kΩ.cm2.