Recrystallization of the cold-deformed discontinuous precipitation microstructure in Al-Zn (-Cu) alloys

摘要

Recrystallization of cold-rolled discontinuous, precipitation microstructure which has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigated by optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallization mechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be divided into coarsening mainly driven by stored deformation energy at colony boundaries and slip bands and the one mainly driven by boundary energy in the area with little deformation. It is shown that the addition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffraction analysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn during the heating process.