Abstract The orientation relationships (ORs), segregation behavior and morphologies of β' precipitate in an over-aged Al-Mg-Si-Cu alloy are systematically characterized by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Six different ORs and two morphologies, i.e. rod- and lath-like are revealed for β' precipitates, and Cu segregation at the β′/α-Al interface is observed in all these precipitates. The rod-like β' precipitate has multiple β'-angles ranging from 6.1° to 14.1° and non-uniform Cu segregation at the β′/α-Al interface, while the lath-like β' precipitate has a constant β'-angle of 0° and a periodic Cu segregation. These different ORs are explained to be attributable to the rotation of QP lattice, a near-hexagonal network of Si columns formed within β' precipitates, which causes different lattice matching of β′ with α-Al lattice. These findings provide new insights in controlling the precipitation hardening and mechanical properties of this type of alloys.

中文翻译：

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Al-Mg-Si-Cu合金中β'相的多重取向关系及形貌

摘要 采用原子分辨率高角度环形暗场扫描透射电子显微镜 (HAADF-STEM) 系统地表征了过时效 Al-Mg-Si-Cu 合金中 β' 析出物的取向关系 (ORs)、偏析行为和形貌。 ）。β' 析出物显示出六种不同的OR 和两种形态，即棒状和板条状，并且在所有这些析出物中都观察到在β'/α-Al 界面处的Cu 偏析。棒状 β' 析出物具有 6.1°~14.1° 的多个 β'-角，在 β'/α-Al 界面处 Cu 偏析不均匀，而板条状 β' 析出物具有恒定的 β'- 0°的角度和周期性的Cu偏析。这些不同的 OR 被解释为可归因于 QP 晶格的旋转，QP 晶格是在 β' 内形成的近六边形 Si 柱网络 析出，这导致 β' 与 α-Al 晶格的不同晶格匹配。这些发现为控制此类合金的沉淀硬化和机械性能提供了新的见解。