The influence of Sc and Zr additions on microstructure and corrosion behavior of AA5182 alloy sheet

Minor additions of Sc and Zr to a 5182 base alloy were used to study the effects of microstructure on the susceptibility to intergranular corrosion (IGC) of 5xxx sheet alloys. The results showed that minor Sc and Zr additions significantly decrease the IGC susceptibility as measured by the depth of IGC for the high-temperature annealed sheet. The improvement in IGC resistance is attributed to a high number density of nano-scaled coherent Al 3 (Sc,Zr) dispersoids which resist recrystallization, and produce a fine subgrain structure. The character of the subgrain structure is critical to prevent the occurrence of continuous intergranular Al 3 Mg 2 precipitates during sensitization. • Minor additions of Sc and Zr significantly declined the IGC susceptibility for high-temperature annealed AA5182 alloy sheet. • Coherent Al 3 (Sc,Zr) dispersoids effectively inhibited the recrystallization of AA5182 alloy sheet during annealing. • The intergranular Al 3 Mg 2 phase precipitated preferentially along high angle grain boundaries. • The subgrain structure can prevent the formation of continuous intergranular Al 3 Mg 2 phase.