Mg-Li alloys with high lithium concentrations possess a lightweight body-centered cubic (BCC) matrix structure (β-Li). Interspersed eutectics (primarily the reticulated I-phase) often form along phase boundaries (PBs) and grain boundaries (GBs) which strengthen the alloy but cause the loss of ductility due to the brittle behavior of I-phase. By modifying the Li content, we fabricated the (β+α) biphase Mg-Li alloy in which the α-Mg phase with a hexagonal close-packed structure (HCP) is embedded in β-Li matrix, significantly increasing interface density. The high-density interfaces mitigate the distribution and dimension of the I-phase along GBs and PBs. The alloy exhibits enhanced ductility (elongation (EL) = 17.8 %) compared with the alloy without the α-Mg phase (EL = 5.1 %). Structural characterizations unveil the strengthening mechanism of the nanoscale B2 (Li, Mg)₃Zn-type precipitates in conjunction with the microscale I-phase. The (Li, Mg)₃ Zn nanophases augment the yield and ultimate tensile strength of the alloy without a discernible compromise in ductility, predominantly due to gliding dislocations cutting through the precipitates. In contrast, the microscale I-phase presents a formidable barrier to dislocation motion, facilitating dislocation pileups at interfaces and culminating in diminished ductility across the interface. In-situ stretching techniques were employed to scrutinize the microstructural evolution of alloys during tensile deformation, elucidating that the deformation compatibility of alloys correlates with the average size of the I-phase and their distribution along GBs and PBs. Corresponding to the orientation relationship (OR) between the α-Mg and β-Li phases {110}Li//{0001}Mg and <$\overline{1}11$$\overline{1}11$>Li //<$11\overline{2}0$$11\overline{2}0$>Mg, the slip continuity between α-Mg and β-Li on plane pairs of {123}Li-{$11\overline{2}2$$11\overline{2}2$}Mg and {112}Li-{$11\overline{2}2$$11\overline{2}2$}Mg assures the deformation compatibility through facilitating the deformation across interfaces. Simultaneously, during the stretching process, the dispersed I-phase instigates the emergence of sporadic microcracks, indicating gradual damage evolution. These discoveries offer novel insights into achieving exceptional strength-ductility amalgamations in Mg-Li alloys through microstructural adjustments.

中文翻译：

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通过分散的 α-Mg 相提高铸造 Mg-Li 合金的延展性，从而减轻沿晶界散布共晶的尺寸和分布


具有高锂浓度的 Mg-Li 合金具有轻质体心立方 （BCC） 基体结构 （β-Li）。穿插的共晶（主要是网状 I 相）通常沿相界 （PB） 和晶界 （GB） 形成，这增强了合金，但由于 I 相的脆性行为导致延展性丧失。通过改性 Li 含量，我们制备了 （β+α） 双相 Mg-Li 合金，其中具有六方密排结构 （HCP） 的 α-Mg 相嵌入 β-Li 基体中，显著提高了界面密度。高密度接口可缓解 I 相沿 GB 和 PB 的分布和维度。与没有 α-Mg 相的合金 （EL = 5.1%） 相比，该合金表现出更高的延展性（伸长率 （EL） = 17.8 %）。结构表征揭示了纳米级 B2 （Li， Mg）₃Zn 型沉淀物与微尺度 I 相结合的强化机制。（Li， Mg）₃ Zn 纳米相提高了合金的产量和极限抗拉强度，而延展性没有明显的妥协，这主要是由于滑动位错切开了沉淀物。相比之下，微尺度 I 相为位错运动提供了强大的屏障，促进了界面处的位错堆积，最终导致界面的延展性降低。采用原位拉伸技术来仔细检查合金在拉伸变形过程中的微观组织演变，阐明合金的变形相容性与 I 相的平均尺寸及其沿 GB 和 PB 的分布相关。对应于 α-Mg 和 β-Li 相之间的取向关系 （OR） {110}Li//{0001}Mg 和 <$\bar{1}11$>Li //<$11\bar{2}0$>Mg，α-Mg 和 β-Li 在 {123}Li-{$11\bar{2}2$}Mg 和 {112}Li-{$11\bar{2}2$}Mg通过促进变形加工来确保变形兼容性ross 接口。同时，在拉伸过程中，分散的 I 相引发了零星微裂纹的出现，表明损伤逐渐演变。这些发现为通过微观结构调整在 Mg-Li 合金中实现卓越的强度-延展性汞齐提供了新的见解。