Enhanced mechanical property and corrosion resistance of alloy 5182 FSW joints by Sc and Zr alloying

Abstract

For conventional work-hardened Al Mg alloys, Friction-Stir Welding (FSW) can soften the as-welded joint, and increase the susceptibility to intergranular corrosion (IGC). This study found that small Sc and Zr additions (0.1wt.%Sc, 0.1wt.%Zr) increased the yield strength of the Al Mg alloy FSW joint by ~50 MPa, and decreased the IGC susceptibility dramatically. The microstructure characterization revealed that strengthening effects derived from fine coherent Al 3 (Sc,Zr) dispersoids and extensive grain refinement contributed to the higher strength of the joint. The improved corrosion resistance in both stir zone (SZ) and heat-affected zone (HAZ) was attributed to the pronounced grain refinement (in SZ) and subgrain structure (in HAZ), respectively. The strong pinning effect of Al 3 (Sc,Zr) dispersoids inhibits recovery and recrystallization in the highly deformed weld microstructure. • Sc and Zr alloying improved strength/corrosion resistance of Al Mg alloy FSW joint. • Coherent Al 3 (Sc,Zr) dispersoids can be preserved in Sc/Zr-added alloy 5182 FSW joint. • Al 3 (Sc,Zr) precipitation and grain boundary strengthening contributed to strength increment. • Both subgrain and finer grain structure can suppress intergranular corrosion.