Dynamic Recrystallization Based on Twinning in Coarse-Grained Mg

Mechanisms of dynamic recrystallization (DRX) associated with twinning are proposed and discussed on the results of microstructure evolution during warm and hot deformation of a coarse-grained Mg. 'Twin' DRX is composed of following elementary processes: i.e. formation of twin boundaries and their transformation into random boundaries followed by their local boundary migration taking place during deformation. The formation of DRX nuclei can result from mutual intersection of deformation twins belonging to primary twinning systems and subdividing of primary twin lamellas by secondary twins or subboundaries. Twin boundaries eventually convert into random boundaries in high strain due to their interaction with mobile dislocations. The new grains formed in twin lamellas are in non-equilibrium states and exhibit almost rectangular shape. A limited boundary migration takes place locally, resulting in development of equiaxed grains in high strain. Under high temperature deformation, when mechanical twinning is suppressed, DRX can also develop through growth of twins presented in an initial structure.