The catalyzing effect on nucleation of recrystallization from existing grains resulting from previous lower temperature deformation is analyzed, analogous to the size effect of foreign nucleus in heterogeneous nucleation. Analytical formulation of the effective nucleation site for recrystallization leads to a negative temperature dependence of recrystallized grain size of metals. Non-isochronal annealing-where annealing time is set just enough for the completion of recrystallization at different temperatures-is conducted on pure copper after severe plastic deformation. More homogeneous and smaller grains are obtained at higher annealing temperature. The good fit between analytical and experimental results unveils the intrinsic feature of this negative temperature dependence of recrystallized grain size.
Keywords: catalyzed nucleation; equal channel angular pressing (ECAP); high angle grain boundary (HAGB); negative temperature dependence; recrystallization.