Effects of Al3(Sc,Zr) and Shear Band Formation on the Tensile Properties and Fracture Behavior of Al-Mg-Sc-Zr Alloy

The mechanical properties and microstructures of Al-6Mg-0.25Sc-0.1Zr alloy ( wt.%) during annealing were investigated by means of uniaxial tensile testing, optical microscope, scanning electron microscope, transmission electron microscope, and high-resolution transmission electron microscope. The results show that a large number of micro and grain-scale shear bands form in this alloy after cold rolling. As the tensile-loading force rises, strain softening would generate in shear bands, resulting in the occurrence of shear banding fracture in cold-rolled Al-Mg-Sc-Zr alloys. Recrystallization takes place preferentially in shear bands during annealing. Due to the formation of coarse-grain bands constructed by new subgrains, recrystallization softening tends to occur in these regions. During low-temperature annealing, recrystallization is inhibited by nano-scale Al-3(Sc,Zr) precipitates which exert significant coherency strengthening and modulus hardening. However, the strengthening effect of Al-3(Sc,Zr) decreases with the increasing of particle diameter at elevated annealing temperature. The mechanical properties of the recrystallized Al-Mg-Sc-Zr alloy decrease to a minimum level, and the fracture plane exhibits pure ductile fracture characteristics.