Void Swelling Enhancement Near Grain Boundaries Driven by the Production Bias

At elevated temperatures, vacancy emission from thermally unstable primary vacancy clusters (PVCs) leads to the shrinkage of the overwhelming majority of primary interstitial clusters (PICs) also produced in collision cascades. Sessile PICs shrinking below a certain minimum size become mobile. In a spatially heterogeneous case, an exact balance between their outflow from any finite volume and the corresponding inflow from adjacent spatial regions is not necessarily maintained, which is particularly important near grain boundaries. The excess of vacancies caused by the net interstitial outflow from a certain volume leads to enhanced void swelling in this volume. In this case, neither the conventional dislocation bias nor the long-range transport of small PICs by one-dimensional glide along close-packed atomic directions is required. This work analyzes and discusses the operation of this mechanism of enhanced void swelling in regions adjacent to grain boundaries.