Factors controlling segregation tendency of solute Ti, Ag and Ta into different symmetrical tilt grain boundaries of tungsten: First-principles and experimental study
Factors controlling segregation tendency of solute Ti, Ag and Ta into different symmetrical tilt grain boundaries of tungsten: First-principles and experimental study
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DOI：
10.1016/j.actamat.2021.116868
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发表时间：
2021-04
期刊：
影响因子：
9.4
通讯作者：
A. T. AlMotasem;T. Huminiuc;T. Polcar
中科院分区：
文献类型：
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作者：
A. T. AlMotasem;T. Huminiuc;T. Polcar
在以往的报道中，实验研究表明晶界偏析可以控制材料的热稳定性和强度。在本研究中，我们利用密度泛函理论（DFT）计算和TEM实验支持，研究了W的溶质（Ti， Ag和Ta）原子在低/高角度对称倾斜晶界（STGBs）上的偏析行为。我们发现，在低角度stgb中，Ti和Ta没有偏析倾向；然而，它们向大角度stgb的核心有轻微的偏析倾向。相反，Ag更容易在GB平面内和周围析出。我们估计了机械和电子对溶液能量的贡献，发现电子贡献占主导地位。此外，利用局域态密度（PDOS）分析了溶质和W原子的d−价电子的作用。我们发现Ta的大量d−价电子杂化在稳定W-Ta键中起重要作用，而W- ti键的各向异性有助于稳定周围的W原子。电荷转移分析表明，Ti和Ta失去电子给W原子。与电负性规律相反，Ag原子从邻近的W原子获得电荷，优异的s - s杂化可以解释Ag原子的GB偏析增加。
In previous reports, experimental studies have shown that both thermal stability and strength can be controlled by grain boundary (GB) segregation. In this study, we investigate the segregation behavior of solute (Ti, Ag and Ta) atoms to low/high-angle symmetric tilt grain boundaries (STGBs) of W using density functional theory (DFT) calculations and supported by TEM experiments. We found no segregation preference for Ti or Ta at low-angle STGBs; however, they exhibit a slight segregation tendency to the core of high-angle STGBs. In contrast, Ag is more prone to segregate in and all around the GB plane. We estimated the mechanical and electronic contributions to solution energy and found that the electronic contribution is dominant. Furthermore, the role of d− valence electrons of solute and W atoms, was analyzed using the local density of states (PDOS). We found that substantial d− valence electrons hybridization in the case of Ta plays an important role in stabilizing W-Ta bonds, while the anisotropic nature of W-Ti bond contributes to stabilize surrounding W atoms. Charge transfer analysis revealed that Ti and Ta lose electrons to W atoms. Contrary to the electronegativity rule, Ag atoms gain charge from neighboring W atoms and excellent s− s hybridization may explain the increased GB segregation of Ag atoms.