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

分类： 材料科学 >> 材料科学（综合） 提交时间： 2022-06-20

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

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 Ʃ5(310) and Ʃ5(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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镓基液态金属热界面材料的性能研究

分类： 动力与电气工程 >> 工程热物理学 提交时间： 2017-06-07 合作期刊: 《工程热物理学报》

高云霞, 刘静, 王先平, 方前锋

摘要： 采用微氧化法制备Ga基室温液态金属热界面材料。实验结果表明，微量氧化镓的存在可显著改善液态金属的润湿性，且GaIn10合金热界面材料具有较高的热导率(~19.2 W/mK)。搭建接触传热测试平台，分别研究液态金属Ga及其二元、三元合金热界面材料的导热性能, 对比市售导热硅脂，该新型镓基热界面材料，特别是其二元合金热界面材料，在大功率下工作时热源温度相对于导热硅脂下降近14 oC, 界面热阻只有5.4 Kmm2/W，显示出更加优越的导热性能。

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