Abstract
1 The extruded Mg-7Li-2Al-1.5Sn alloy possesses good mechanical properties with the yield strength, ultimate tensile strength and elongation of 250 MPa, 324 MPa and 11.9% at room temperature, respectively. 2 Dynamic precipitation and dynamic recrystallization occur during hot deformation. Nanoscale Sn-rich precipitates with a size of ∼14 nm are formed and the average size of DRXed grains in the extruded Mg-Li-Al-Sn alloys is ∼2 μm. 3 The strengthening mechanism of the extruded alloy mainly consists of grain boundary, precipitation and dislocation strengthening. Grain boundary strengthening is the most dominant mechanism in the test alloy. 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, LiMgAl 2 , Mg 2 Sn and Li 2 MgSn 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 (Mg 2 Sn and Li 2 MgSn) 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.
Published Version
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