摘要:
采用基于密度泛函理论的第一性原理,研究了稀土La对bcc-Fe中Cu析出行为的影响。计算了α-Fe中La原子和Cu原子与空位之间,以及La原子和Cu原子之间的点缺陷结合能；在此基础上,讨论了α-Fe中La对Cu扩散激活能的关系。结果表明： La原子与空位之间有较强的相互吸引作用,且对近邻Cu原子也有一定的束缚。此外, La的加入使Cu原子近邻的空位形成能显著升高,这表明La, Cu 偏聚区形成空位较为困难。与此同时,由于La原子对近邻空位和Cu原子的吸引作用,使Cu原子向近邻空位跳跃的迁移能有所升高。迁移能与空位形成能变化的计算结果显示, La原子的加入能够使α-Fe中Cu的扩散激活能显著升高,从而延缓了铁素体区富铜相的偏聚和析出。
关键词:
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La
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bcc-Fe
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Cu
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扩散
Abstract:
The influence of La on the Cu precipitation in bcc-Fe is determined by first-principles density functional calculations. The binding energies of La-vacancy, Cu-vacancy pairs, and La-Cu pair are calculated, and the effects of La atoms on the diffusion activation energy of Cu atoms in bcc-Fe are considered. It is found that there exist strong attractive interactions between La atom and vacancy and between La atom and adjacent Cu atom. In addition, the formation energy of the vacancy adjacent to Cu atom increases significantly with the La addition, suggesting that vacancy is di?cult to form in the La and Cu segregation zone. Meantime, we find that the migration energy of Cu atom is enhanced due to the attractions of La atom to adjacent vacancy and Cu atom. The calculated results of the vacancy formation energy and migration energy indicate that Cu atom possesses a higher diffusion activation energy after the La addition, and in turn, delays the segregation and precipitation process of the Cu rich phase in bcc-Fe.
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