Grain refinement in a commercial Al-Mg-Sc alloy under hot ECAP conditions

Grain refinement taking place during equal-channel angular pressing (ECAP) was studied in a commercial Al-6% Mg-0.4% Mn-0.3% Sc alloy at a temperature of 450 °C (∼0.8Tm) to demonstrate the feasibility of obtaining new fine-grained structure in a hard-to-deform Al-Mg-Sc alloy under hot intense plastic straining (IPS) conditions and investigate the evolution process of new grains. Inhomogeneous deformation occurring during hot ECAP leads to formation of deformation bands. Repeated ECAP results in mutual crossing and increase in number and the misorientation of deformation bands, followed by transformation of the boundaries of deformation bands into high-angle ones. As a result, a new fine-grained microstructure with an average crystallite size of 2.8 μm develops at large strains above 8. It is concluded that grain refinement occurs in accordance with deformation-induced continuous reactions; that is similar to in-situ or continuous dynamic recrystallization. The mechanisms of new grain evolution, as well as factors promoting grain refinement, are discussed in detail.