On the annealing of dislocation loops by climb

It is pointed out that the only case where the shrinkage rate of a climbing dislocation loop can be predicted without making detailed and untested assumptions about climb processes in the core is the limiting case where the creation and destruction of point defects in the core are rapid enough so that somehow the core is capable of acting as an “ideal source” with the capability of maintaining local detailed balance with defects in the lattice. Under these conditions it is found that loop shrinkage, even in thin films suitable for transmission electron microscopy, should usually occur under diffusion controlled conditions. Our present lack of knowledge regarding the variety of mechanisms by which the ideal source condition can be achieved is emphasized. The detailed and specific climb model of Silcox and Whelan, which has been universally employed in the literature in the treatment of this problem, is shown to depend upon a number of restrictive and untested assumptions. It is shown however that this climb model predicts a shrinkage rate which is almost exactly the same as that of an ideal source climbing under diffusion controlled conditions. Selected experimental data are discussed. Anomalies in the recent experimental data of Edington and Smallman for the shrinkage of hexagonal faulted loops are pointed out.