【摘要】 本文利用原子分辨的高角环形暗场扫描透射电镜（HADDF-STEM）成像技术并结合第一性原理计算的方法研究了Mg₉₇Gd₂Y₁（at.%）合金200℃时效初期结构的形成和演变过程。结果表明,合金时效初期优先形成与富稀土原子柱近邻组合关联的各种纳米级细小富稀土团簇。这些由富稀土原子柱构建的团簇可以通过分解、重组而转变成β′′型局域网格状析出以及"之"字形G.P.区,进而形成β′相晶核。通过对具有典型构型的析出团簇形成能和结合能的计算,进一步验证了合金时效初期结构演变过程的合理性。更多还原

【Abstract】 Atomic-resolution high-angle annular dark-field scanning（HAADF-STEM） imaging technique and first-principles calculation method have been applied to investigate the formation and evolution of the early-stage precipitation structures in the Mg₉₇Gd₂Y₁（at. %） alloy aged at 200 ℃. The results show that nano-sized clusters constructed by Gd/Y-rich columns with various coupling configurations are preferentially formed at the very early aging stage. These precipitation clusters could undergo re-dissolving and re-arranging processes involving with their constitution Gd/Y-rich atomic columns during the aging proceeding, which allow to transform into the local Gd/Y-rich column network of β″-type and zig-zag G.P. zones, and further into β′ nuclei. The calculated results on the formation and binding energies for the precipitation clusters with various typical Gd/Y-rich column configurations can also verify that the inferred evolution process of the early aging structures is plausible.更多还原