材料科学
晶界
双层
镍
晶间腐蚀
凝聚态物理
杂质
铜
亚稳态
铋
相(物质)
化学物理
冶金
合金
微观结构
化学
有机化学
物理
生物化学
膜
作者
Joongoo Kang,Greg C. Glatzmaier,Su-Huai Wei
标识
DOI:10.1103/physrevlett.111.055502
摘要
Ductile metals such as Ni and Cu can become brittle when certain impurities (e.g., Bi) diffuse and segregate into their grain boundaries (GBs). Using first-principles calculations, we investigate the microscopic origin of the Bi-induced loss of cohesion of Ni and Cu GBs. We find that the Bi bilayer interfacial phase is the most stable impurity phase under the Bi-rich condition, while the Bi monolayer phase is a metastable phase regardless of the value of the Bi chemical potential. Our finding is consistent with the recent experimental observation for Ni GBs [Luo et al. Science 333, 1730 (2011)]. The electric polarization effect of the Bi bilayer substantially enhances the strength of the Bi-metal interfacial bonds, stabilizing the bilayer phase over other phases. The Bi-Bi interlayer bonding is significantly weakened in the GBs, leading to a factor of 20 to 50 decrease in the GB cohesion, which has strong implications for the understanding of Bi-induced intergranular fracture of Ni and Cu polycrystals.
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