Duplex-structured Mg-7Li-2Al-1.5Sn alloys with high strength were fabricated and their strengthening mechanism was investigated. The Mg-7Li-2Al-1.5Sn alloys were prepared by casting and extruded at the temperature of 533 K with an extrusion ratio of 25:1. The microstructure and mechanical properties of Mg-7Li-2Al-1.5Sn alloys were systematically investigated by OM, XRD, SEM, TEM, and tensile tests. The results show that Mg-7Li-2Al-1.5Sn alloys are mainly composed of α-Mg, β-Li, LiMgAl₂, Mg₂Sn and Li₂MgSn phases. The yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the extruded alloy at room temperature reach 250 MPa, 324 MPa and 11.9%, respectively. A lot of Sn-rich precipitates (Mg₂Sn and Li₂MgSn) are precipitated during extrusion with an average size of ∼14 nm, which is beneficial to the grain refinement. Dynamic recrystallization occurs during hot deformation and the nano-precipitates effectively refine the dynamic recrystallized (DRXed) grains. Besides, the residual dislocations existed in DRXed and un-DRXed grains result in the dislocation strengthening in the extruded alloy. Mg-7Li-2Al-1.5Sn alloys possess excellent high-temperature mechanical properties with the YS, UTS and EL of 200 MPa, 237 MPa and 26.7% at 423 K, respectively. Sn-rich precipitates with good thermal stability can effectively prevent grain growth, which is good for the improvement of the high-temperature performance of Mg-Li-Al-Sn alloy.

制备了高强度双相结构的Mg-7Li-2Al-1.5Sn合金并研究了其强化机制。Mg-7Li-2Al-1.5Sn 合金是通过铸造和挤压制备的，在 533 K 的温度下，挤压比为 25:1。通过OM、XRD、SEM、TEM和拉伸试验系统地研究了Mg-7Li-2Al-1.5Sn合金的显微组织和力学性能。结果表明，Mg-7Li-2Al-1.5Sn合金主要由α-Mg、β-Li、LiMgAl ₂、Mg ₂ Sn和Li ₂ MgSn相组成。挤压合金在室温下的屈服强度（YS）、极限拉伸强度（UTS）和伸长率（EL）分别达到250 MPa、324 MPa和11.9%。大量富锡沉淀物（Mg ₂ Sn 和 Li ₂MgSn)在挤压过程中析出，平均粒径约为 14 nm，有利于晶粒细化。在热变形过程中发生动态再结晶，纳米沉淀有效地细化动态再结晶 (DRXed) 晶粒。此外，DRXed 和un-DRXed 晶粒中存在的残余位错导致挤压合金中的位错强化。Mg-7Li-2Al-1.5Sn 合金具有优异的高温机械性能，在 423 K 时的 YS、UTS 和 EL 分别为 200 MPa、237 MPa 和 26.7%。具有良好热稳定性的富Sn析出物可有效阻止晶粒长大，有利于提高Mg-Li-Al-Sn合金的高温性能。