Crystal structure and stability of complex precipitate phases in Al–Cu–Mg–(Si) and Al–Zn–Mg alloys
Crystal structure and stability of complex precipitate phases in Al–Cu–Mg–(Si) and Al–Zn–Mg alloys
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DOI：
10.1016/s1359-6454(01)00229-4
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发表时间：
2001-09
期刊：
影响因子：
9.4
通讯作者：
C. Wolverton
中科院分区：
文献类型：
--
作者：
C. Wolverton
我们演示了如何第一性原理的总能量计算可以用来阐明多组分铝合金中复杂沉淀物的晶体结构和形成过程。对于沉淀物S（Al-Cu-Mg）、η '（Al-Zn-Mg）和Q（Al-Cu-Mg-Si），计算了文献中可用的每种晶体结构模型的能量，以便对有效性进行严格评估模型。在所有三个系统中，还计算了固溶体相以及其他关键相（例如，平衡相，GP区）。对于S和η′相，我们发现最近提出的结构（基于电子显微镜）产生不合理的高能量，因此我们建议重新评估这些模型。然而，对于所有三种沉淀物，我们发现，基于X射线衍射细化的结构提供了合理的能量和结构参数，因此第一原理的结果支持这些结构细化。此外，我们预测能量降低网站职业和化学计量的沉淀相，实验信息是不完整的。这项工作表明，第一性原理总能量计算可以在未来作为一种补充技术与衍射或显微镜研究沉淀物的结构和稳定性。
We demonstrate how first-principles total energy calculations may be used to elucidate both the crystal structures and formation enthalpies of complex precipitates in multicomponent Al alloys. For the precipitates, S(Al–Cu–Mg), η′ (Al–Zn–Mg), and Q(Al–Cu–Mg–Si), energetics were computed for each of the models of the crystal structures available in the literature allowing a critical assessment of the validity of the models. In all three systems, energetics were also calculated for solid solution phases as well as other key phases (e.g., equilibrium phases, GP zones) in each precipitation sequence. For both the S and η′ phases, we find that recently proposed structures (based on electron microscopy) produce unreasonably high energies, and thus we suggest that these models should be re-evaluated. However, for all three precipitates, we find that structures based on X-ray diffraction refinements provide both reasonable energetics and structural parameters, and therefore the first-principles results lend support to these structural refinements. Further, we predict energy-lowering site occupations and stoichiometries of the precipitate phases, where experimental information is incomplete. This work suggests that first-principles total energy calculations can be used in the future as a complementary technique with diffraction or microscopy for studying precipitate structures and stabilities.