A New Theory of Recrystallization Nuclei

Abstract

After a review of the numerous experimental observations in this field which need to be explained, a new theory is presented of nucleus formation when a cold-worked metal is annealed. The nuclei are held to be formed in the most distorted parts of the lattice, in the `local curvatures' postulated by Burgers. At these places the lattice locally regains its perfection by the recently discovered process of diffusion of dislocations, or `polygonization', and the perfect nucleus so created is then able to consume the less perfect crystal in its vicinity. Experimental evidence for this picture is presented. Each potential nucleus is held to have a definite incubation period (as distinct from the fixed probability of becoming active which was the basis of previous theories). By means of certain assumptions as to the distribution of curvatures and the dependence of incubation time on curvature, a quantitative theory is developed, which is found to be capable of accounting for all the experimental data on nucleation rates. The paper concludes by comparing critically the new theory with older ones.