Abstract A kind of needle-like sandwich-combined precipitation product (denoted as η) was found to be formed concurrently with the equilibrium β-phase in a Mg-Gd-Y alloy subjected to duplex aging at 200°C and 250°C, respectively, and its structure was characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) technique. It had been clearly revealed that the η-precipitate consists of a new base-centered orthogonal (BCO) precipitate as a long core (B) which is invariably sandwiched by the face-centered cubic (FCC) Gd(Y) solute precipitate platelets (F) as surface-shells. The orientation relationships involved with the unique F-B-F sandwiched precipitation for the η constructing in the Mg matrix were determined to be 001 > F / / , 001 > B , { 010 } F / / { 010 } B and 100 > F / / 0001 > Mg , { 010 } F / / { 10 1 ¯ 0 } Mg , respectively.

中文翻译：

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双时效Mg-Gd-Y合金中形成的一种夹心复合析出物

摘要 Mg-Gd-Y 合金在 200°C 和 250°C 双重时效时，在平衡 β 相的同时形成了一种针状夹心复合析出产物（用 η 表示），分别采用高角度环形暗场扫描透射电子显微镜（HAADF-STEM）技术对其结构进行表征。已经清楚地表明，η-沉淀物由作为长核（B）的新碱心正交（BCO）沉淀组成，它总是夹在面心立方（FCC）Gd（Y）溶质沉淀片之间（ F) 作为表面壳。与 Mg 基体中 η 构造的独特 FBF 夹层沉淀所涉及的取向关系被确定为 001 > F // , 001 > B , { 010 } F // { 010 } B 和 100 > F // 0001 >镁