On the theory of bubble coarsening in metals

A comprehensive analysis of simulation results obtained recently by the authors in modeling of gas bubble evolution driven by the Ostwald ripening process in irradiated metals has been carried out. Relevant experimental data characterized by a relatively small mean bubble radius measured in a range of about 1-5 nm in stainless steel specimens containing 100 appm He and annealed at 1023 K have also been used in this study. A comparison of both the experimental and simulation data with analytical estimations predicted by the original theory at the late stage of bubble coarsening was considered unsatisfactory. To overcome this inconsistency, a new approach has been applied assuming that bubbles evolve at significantly different rates at either earlier or later stages of the process. Despite the difference of the rates in these cases, a complete similarity of corresponding asymptotic bubble size distributions has been detected. Experimentally observable time dependences of bubble density and mean bubble radius agree well with the recent modeling and our present analysis results. This indicates that Ostwald ripening provides a reasonable explanation for bubble evolution during annealing. Unlike the conventional interpretation of bubble coarsening, growing bubbles attain chemical equilibrium with interstitial gas emitted by shrinking bubbles. It is this assumption which allows for getting the asymptotic bubble size distribution function similar to that given by the classical theory of Ostwald ripening. (C) 2019 Elsevier B.V. All rights reserved.