Enhancing strength and stress corrosion cracking resistance in high-Mg Al-Mg alloys through nanostructuring and controlled annealing

Abstract

The strength of traditional Al-Mg alloys primarily depends on cold deformation and increasing Mg content, but it can become susceptible to stress corrosion cracking (SCC) when the Mg content is high (>3 wt.%). Simultaneous optimizing strength and SCC resistance in Al-Mg alloys is challenging. This study introduces a nanostructured Al-10Mg (10 wt.%) alloy with improved strength and SCC resistance by dynamic plastic deformation and optimized annealing. The as-deformed sample exhibits a nano-scaled lamellar structure. With rising annealing temperatures, structure size of the alloy increases while dislocation density decreases, transitioning lamellar to equiaxed grains. Nanostructured Al-10Mg alloys annealed at 250°C exhibit superior mechanical properties and reduced SCC susceptibility at sensitization state. The high fraction of low-angle grain boundaries with a reduction in dislocation density can effectively suppress the nucleation and growth of grain boundary precipitates (GBPs) during sensitization, thereby maintaining a relatively low GBPs coverage. The results provide guidance for designing Al-Mg alloys that are stronger and more resistant to SCC with higher Mg content.