On the corrosion of additively manufactured aluminium alloy AA2024 prepared by selective laser melting

Abstract

The microstructure, and electrochemical properties of additively manufactured Al-alloy AA2024 (AM2024, Al-Cu-Mg) produced by selective laser melting are reported. In-depth microstructural characterisation was conducted to compare the resultant microstructure, including phase identification, size and distribution, against the wrought counterpart AA2024-T3. The prospect of producing net shape Al-alloys via additive manufacturing (AM) has the potential to provide cost effective and high specific strength components. It was revealed that the dominant second phase formed in AM2024 was Al2Cu (θ–phase), in contrast to the typical Al2CuMg (S-phase) observed in AA2024-T3. The AM2024 also revealed a refined microstructure, with an average constituent particle size < 1 μm. Thermodynamic calculations revealed that the preferential formation of θ-phase was influenced by the Si content of AM2024 (0.78 wt. %). Atomic emission spectroelectrochemistry (AESEC) measurements revealed a lower Al dissolution rate (5 times) in the case of AM2024. Anodic polarisation revealed that AM2024 was capable of forming an appreciable surface oxide relative to AA2024-T3. The findings herein demonstrate the possibilities of AM as applied to a high strength Al-alloy.