Abstract We report a combined experimental and first principles study of an extremely immiscible alloy of Mo with 1 and 2 at.% Na, which was produced by high-energy ball milling. The microstructure of the as-milled and annealed state were examined by various methods, including atom-probe tomography (APT), transmission electron microscopy, and energy-dispersive (EDX) analysis. Despite the complete immiscibility of the Mo-Na system in the solid and even in the liquid state, APT measurements clearly evidence the formation of a true nanocrystalline solid-solution microstructure with insignificant Na clustering for samples with 1 at.% Na. In agreement with our x-ray diffraction experiments, first principles calculations expose that the Na atoms do not expand the Mo lattice, which is in contrast to predictions using Vegard's rule. Heating at 700 °C induces only slight grain growth while the solid solution remains remarkably stable without any decomposition. On the contrary, after annealing at 900 °C first Na segregations at triple junctions and significant grain growth are observable, although the solid solution still retains most of the dissolved Na.

中文翻译：

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钼和钠的非平衡固溶体：原子尺度实验和第一性原理研究

摘要 我们报告了对通过高能球磨生产的具有 1 和 2 at.% Na 的极其不混溶的 Mo 合金的实验和第一性原理研究。通过各种方法检查研磨和退火状态的微观结构，包括原子探针断层扫描 (APT)、透射电子显微镜和能量色散 (EDX) 分析。尽管 Mo-Na 系统在固态甚至液态中完全不混溶，但 APT 测量清楚地证明了真正的纳米晶固溶体微观结构的形成，对于含 1 at.% Na 的样品来说，Na 团簇微不足道。与我们的 X 射线衍射实验一致，第一性原理计算表明 Na 原子不会扩展 Mo 晶格，这与使用 Vegard 规则的预测相反。在 700 °C 加热仅引起轻微的晶粒生长，而固溶体保持非常稳定，没有任何分解。相反，在 900 °C 退火后，可以观察到三重结处的第一次 Na 偏析和显着的晶粒生长，尽管固溶体仍然保留了大部分溶解的 Na。