Thermodynamic study of the critical nucleus size for metadynamic recrystallisation

On the basis of thermodynamics, it is shown that the critical nucleus size for metadynamic recrystallisation is smaller than that for dynamic recrysta llisation. It follows that the nucleation rate of metadynamic recrystallisa tion is not zero. A Cr25Ti steel was hot deformed and its recrystallised st ructures were examined after delayed quench. It was observed that after the deformation was terminated, both the grain size and the subgrain size decr eased at first, although the grains eventually coarsened at longer times. T his is attributed to the conversion of potential embryos formed during dyna mic recrystallisation into true nuclei in metadynamic recrystallisation. Th e results from the experiment appear to be consistent with the theoretical analysis. (C) 2000 Elsevier Science S.A. All rights reserved.