Quantifying grain boundary damage tolerance with atomistic simulations

摘要

Grain boundaries play a pivotal role in defect evolution and accommodation within materials. Irradiated metals have been observed to form defect denuded zones in the vicinity of grain boundaries. This is especially apparent in nanocrystalline metals, which have an increased grain boundary concentration, as compared to their polycrystalline counterparts. Importantly, the effect of individual grain boundaries on microstructural damage tolerance is related to the character or structural state of the grain boundary. In this work, the damage accommodation behavior of a variety of copper grain boundaries is studied using atomistic simulations. Damage accumulation behavior is found to reach a saturation point where both the free volume and energy of a grain boundary fluctuate within an elliptical manifold, which varies in size for different boundary characters. Analysis of the grain boundaries shows that extrinsic damage accommodation occurs due to localized atomic shuffling accompanied by free volume rearrangement within the boundary. Continuous damage accumulation leads to altered atomic structural states that oscillate around a mean non-equilibrium state, that is energetically metastable. Our results suggest that variation of grain boundary behavior, both from equilibrium and under saturation, is directly related to grain boundary equilibrium energy and some boundaries have a greater propensity to continually accommodate damage, as compared to others.