Exceptional stress corrosion cracking resistance of additively manufactured aluminum alloys in simulated marine environments

• Additive manufacturing (AM) process affects Nano/microstructure in Al-Mg alloys. • Enhanced solid solubility forms a supersaturated solid solution (SSS) during AM. • Solutes in SSS boost strength in AM specimens more effectively than wrought ones. • AM specimens show superior resistance to stress corrosion cracking (SCC). • The absence of β phase in AM alloy reduces H-trapping and crack initiation risks. In this study, an Al–Mg alloy was manufactured using the laser powder bed fusion (L-PBF) additive manufacturing method. A combination of numerical calculations and atomic/microstructural observations revealed that the complex interactions between the laser and metal during L-PBF generate dynamic temperature gradients, rapid solidification, and high cooling rates. These thermal variations significantly influence the nano- and microstructure of the additively manufactured Al–Mg alloys, leading to enhanced solid solubility. Under rapid cooling, the nucleation of second-phase particles is suppressed due to the formation of a supersaturated solid solution, with solute atoms trapped within the matrix. This contributes to substantial solid solution strengthening, resulting in increased yield strength and work hardening rate. Importantly, the additively manufactured (AM) samples demonstrate superior resistance to stress corrosion cracking and intergranular corrosion compared to conventional wrought alloys of similar chemical composition. This improvement is primarily attributed to the absence of electrochemically active β-phase particles at grain boundaries in AM samples. In conventional wrought alloys, these β-phases act as hydrogen sources, promoting hydrogen generation at grain boundaries and leading to intergranular cracking via a hydrogen-enhanced decohesion mechanism.