Influence of pre-recovery on the recrystallization of pure tantalum
Résumé
In order to study the influence of recovery, various pre-recovery treatments at different temperatures followed by a recrystallization treatment are performed on deformed microstructures of pure tantalum. Electron backscatter diffraction is used to characterize deformed and annealed microstructures. Analysis reveals that intergranular deformation strongly depends on the crystallographic orientation. In particular, dislocation content and development of dislocation substructures are the highest for γ-fiber grains. Subsequent recrystallization is affected by this orientation dependence: nucleation is favored in these grains and γ-fiber recrystallized grains are the largest. Pre-recovery affects recrystallization differently depending on initial plastic strain, temperature and time. For low- and moderately-deformed specimens, pre-recovery at low temperature or for short-time favors recrystallization due to more mobile subboundaries which enhance nucleation. Conversely, pre-recovery at high temperature or for long-time disfavors recrystallization due to the prevalence of stored energy decrease over the nucleation enhancement. Recovery is discussed on the basis of those two mechanisms. For highly deformed specimens, pre-recovery leads to a finer recrystallized microstructure whatever the temperature and the time of the treatment.