Corrosion behaviour of novel Al-Fe-Zr alloy developed for additive manufacturing

This study investigates the corrosion behaviour of an additively manufactured (AM) Al-Fe-Zr alloy produced by laser-based powder bed fusion (PBF-LB). The alloy was developed to target high strength and conductivity applications and as a substitute for conventional 6xxx series alloys, which suffer from hot cracking during PBF-LB processing. Multiscale characterization (SEM, EBSD, SKPFM, XPS, and electrochemical testing) revealed that the rapid solidification during PBF-LB produces a highly refined microstructure with nanoscale Fe-Al intermetallic particles (IMPs), resulting in a narrow surface Volta potential range. These features contribute to enhanced electrochemical homogeneity and reduced susceptibility to localized corrosion compared with conventional AA6060. Potentiodynamic polarization tests in NaCl solution indicated comparable overall performance between the AM Al-Fe-Zr alloy and AA6060, while immersion tests demonstrated that the AM alloy exhibited lower pitting susceptibility, attributed to microstructural refinement and the modified composition of the native oxide film. XPS analysis confirmed the incorporation of Fe- and Zr-based oxides into the native film, potentially improving stability and supporting the enhanced corrosion resistance of the AM alloy. Nonetheless, heterogeneities were observed at the level of the melt pools, with the melt pool boundaries (MPBs) presenting coarser IMPs and inclusion-free zones (IFZs). These regions acted as preferential sites for localized attack, occasionally aligning corrosion along MPBs.