Influence of Friction Stir Welding and Post-Weld Aging on Corrosion Behavior of LPBF A20X Alloy

Laser powder bed fusion (LPBF) enables the production of high-strength A20X aluminum components with complex geometries for aerospace applications. However, the limited build volume of LPBF systems often requires separately manufactured parts to be joined. This study compares the microstructure and corrosion behavior of LPBF A20X under four material conditions: base material (BM), as-welded stir zone (SZ), solution-treated and peak-aged base material (BM–PA), and solution-treated and peak-aged stir zone (SZ–PA). Microstructural evolution was assessed using electron microscopy and X-ray diffraction, while corrosion behavior was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization in 3.5 wt.% NaCl solution. Among the tested specimens, BM exhibited the lowest corrosion current density (0.703 μA/cm²), followed by SZ (0.966 μA/cm²), BM–PA (2.257 μA/cm²), and SZ–PA (3.181 μA/cm²). The impedance response and post-polarization SEM observations indicated lower corrosion resistance after solution treatment and aging, particularly in SZ–PA. These findings are consistent with a possible contribution from micro-galvanic interactions involving redistributed and precipitated Cu-rich constituents, TiB₂ particles, and the Al matrix. Under the tested conditions, post-weld heat treatment reduced corrosion resistance compared to FSW alone. This underlines the need to optimize welding and heat-treatment parameters for LPBF A20X components.