Controlling Factors for the Formation of Guinier-Preston Zones in Al-Cu Alloys: An Atomistic Study
Controlling Factors for the Formation of Guinier-Preston Zones in Al-Cu Alloys: An Atomistic Study
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DOI：
10.2320/jinstmet.j2016029
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发表时间：
2016-01-01
影响因子：
0.5
通讯作者：
Ogata, Shigenobu
中科院分区：
文献类型：
--
作者：
Nakagami, Yushi;Kimizuka, Hajime;Ogata, Shigenobu
溶质原子的纳米级析出物通常被称为“Guinier-Preston (GP) 区”，已知在铝合金的沉淀硬化效应中发挥着重要作用。在本研究中，通过提取和检查 Cu 的团内和团簇间相互作用能，研究了分别在 Al-Cu 系统老化早期和中期观察到的 GP1 和 GP2 区中溶质纳米团簇形成的控制因素。在Al中使用密度泛函理论（DFT）计算的Cu的二体和三体结合能表明，Cu-Cu对倾向于在第一最近邻（1NN）位置处结合，并且Cu-Cu三元组在能量上更倾向于在同一{100}平面上包含两个Cu-Cu对的三角形原子团的排列。化学（电荷局域化）效应导致沿 {100} 平面的 GP1 区域中发现的簇间相互作用能也基于 DFT 进行了计算。结果表明，能量上优选的构型是两个平面簇以 2a 的簇间距离排列（其中 a 是 Al 的晶格常数）；值得注意的是，该距离与 Al 的基本结构中的距离相同。实验中观察到的稀铝-铜体系的潜在模型基于提取的簇内和簇间相互作用，然后应用于预测有限温度下铜原子的平面偏析，结果成功地再现了特定温度范围内平面铜簇的形成和两个平面簇的排列。铝铜系。
Nanosized precipitates of solute atoms, which are often called "Guinier-Preston (GP) zones,'' are known to play a significant role in the precipitation-hardening effect on the Al alloys. In this study, the controlling factors for the formation of solute nanoclusters as in GP1 and GP2 zones, which are observed in the early and middle stages, respectively, of aging in the Al-Cu system, were investigated by extracting and examining the intra-and intercluster interaction energies of Cu in Al using density functional theory (DFT). DFT-calculated two-and three-body binding energies for Cu indicated that a Cu-Cu pair tends to bind at the first nearest-neighbor (1NN) positions, and a Cu-Cu. Cu triplet energetically prefers the arrangement of the triangular atomic cluster that contains two Cu-Cu pairs at the 1NN positions on the same {100} plane. Such a characteristic short. range ordering was suggested to be dominated by attractive three. body interactions due to the chemical (charge localization) effect, leading to planar clustering as found in the GP1 zones along the {100} planes. Intercluster interaction energies between two Cu planar clusters in Al were also calculated based on DFT. The results indicated that the energetically preferable configuration was the one in which two planar clusters are aligned at an intercluster distance of 2a (where a is the lattice constant of Al); it is noteworthy that this distance was the same to that in the basic structures of the GP2 zones observed in the experiments. A potential model for a dilute Al-Cu system was constructed on the basis of the extracted intra. and intercluster interactions, and then applied to atomistic Monte Carlo modeling for predicting the planar segregation of Cu atoms at finite temperatures. As a result, the formation of planar Cu clusters and the alignment of two planer clusters separated by 2a were successfully reproduced within a specific temperature range. This demonstrated that these interactions were important controlling factors for the formation of a characteristic pattern of solute clusters in the Al-Cu system.