基于从头算浓度波理论和原子模拟的三元Cu-Ni-Al合金中L1₂有序γ'-Ni₃Al析出相的形成
Formation of $\mathrm{L}1_2$-ordered $γ'$-$\mathrm{Ni}_3\mathrm{Al}$ precipitates in ternary Cu-Ni-Al alloys modelled using an ab initio concentration wave theory and atomistic simulations
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中文总结 AI 辅助
本研究结合从头算浓度波理论与原子模拟，揭示三元Cu-Ni-Al合金中L1₂有序γ'-Ni₃Al析出相的三种成分依赖相变行为，建立了适用于多组元置换合金的高效计算工作流程。
中文摘要 AI 辅助
析出强化型Cu-Ni-Al合金因具有技术应用价值而受到关注，原因在于相干的L1₂有序γ'-Ni₃Al析出相可赋予材料高机械强度，同时保留纯Cu的诸多优良传输特性。本研究针对伪二元体系Cuₓ(Ni₃/₄Al₁/₄)₁₋ₓ（0≤x≤1）的热力学与相稳定性展开研究，采用结合第一性原理电子结构计算与浓度波分析的计算建模框架，从中提取原子间有效对相互作用，用于原子蒙特卡罗模拟。建模结果揭示了三种与成分相关的 distinct 相行为区域，与实验测定的相图定性一致：低Cu含量时，Cu可溶于L1₂有序Ni₃Al相，仅存在Ni与Al之间化学有序的单一可识别相变；中间成分时，该高温有序过程后，低温下发生Cu与L1₂有序Ni₃Al的相分离；高Cu含量时，L1₂有序Ni₃Al直接从固溶体中析出，无明确可识别的次级相变。本研究将这些相变与所考虑合金的基础电子结构特征相关联，证明了一种计算高效的工作流程，可捕捉多组元置换合金中的化学有序与相干析出，对析出强化等现象的研究具有重要意义。
英文摘要
Precipitation-strengthened Cu-Ni-Al alloys are of interest for technological applications because coherent, $\mathrm{L}1_2$-ordered $γ'$-$\mathrm{Ni}_3\mathrm{Al}$ precipitates can confer high mechanical strength while allowing the material to retain many of the good transport properties characteristic of elemental Cu. In this work, we study the thermodynamics and phase stability of the pseudobinary $\textrm{Cu}_x (\textrm{Ni}_{3/4} \textrm{Al}_{1/4})_{1-x}$ system, $0 \leq x \leq 1$. We use a computational modelling framework combining first-principles electronic structure calculations with a concentration wave analysis from which atom-atom effective pair interactions are extracted for use in atomistic Monte Carlo simulations. Our modelling reveals three distinct, composition-dependent regimes of phase behaviour, in qualitative agreement with the experimentally determined phase diagram. At low Cu content, Cu is soluble in the $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$ phase, with a single identifiable phase transition corresponding to chemical ordering between Ni and Al. At intermediate compositions, this high-temperature ordering is followed at lower temperatures by phase separation of Cu and $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$. Finally, at high Cu content, $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$ precipitates directly from the solid solution, with no clearly identifiable secondary transition. We relate these phase transformations to features of the underlying electronic structures of the considered alloys. Overall, this work demonstrates a computationally efficient workflow capturing both chemical ordering and coherent precipitation in multicomponent substitutional alloys, with relevance to the study of phenomena such as precipitation strengthening.
