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Structure, energetics and kinetics of metallic grain boundary nano-voids and corresponding discrete model studied by multiscale and differential evolution simulations

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[英文摘要]The behavior of nano-voids composed of vacancies (Vs) at grain boundaries (GBs) is fundamental to the design of the radiation tolerance of poly-crystalline metals (PCs) via GB engineering. In this study, based on differential evolution, a framework for determining the stable structure of GB nano-voids is developed. Combining the framework with multiscale simulations, we elucidate the vacancy-accumulation and GB void
formation mechanism under irradiation. A GB-structure dependent picture is revealed. At special coincidence-site-lattice (CSL) GBs of ?5(310) and ?5(210) with a medium V-GB binding energy, the V could be reemitted from the GB and also has driving force to be clustered at the GB, developing particularly stable V-clusters from a linear configuration to a platelet and finally to three-dimensional void that has large strain fields in iron with small bulk modulus and a bulk-void alike structure in the GB with large bulk modulus. A group of vacancies reconstruct their positions during the growth. The ripening is also mediated by the mobility of small V-clusters in addition to free Vs. General high-angle and low-angle GBs trap Vs efficiently, where V-clusters only align one-dimensionally or hardly nucleate. Based on the bonding among the vacancies and their neighboring atoms of a nano-void, we propose a high-accuracy predictive linear energetic model applied to the nano-void both at the iron/molybdenum/tungsten GBs and in the grain interior. The model captures the anisotropic feature of a nano-void and reproduces the oscillated vacancy energy level near a nano-void, showing distinct advantages over conventional continuum model and Wulff construction based energy model. Finally, the collective behavior of multiple GBs plays a role in the GB void formation. The present work offers fundamental mechanistic insights to GB nano-void formation and growth and sets a key step towards GB-void prevention in PCs by reducing the fraction of special CSL-GBs.

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From: 李祥艳
DOI:10.12074/202206.00163
Recommended references: 李祥艳,李小林,张艳革,许依春,吴学邦,谢卓明,王先平,潘必才,刘长松,方前锋,陈俊岭,罗广南,王志光.(2022).Structure, energetics and kinetics of metallic grain boundary nano-voids and corresponding discrete model studied by multiscale and differential evolution simulations.[ChinaXiv:202206.00163] (Click&Copy)
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[V1] 2022-06-20 17:09:49 chinaXiv:202206.00163V1 Download
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