Effects of Al element addition on the microstructure and mechanical properties of Mg–Li–Sn alloy

High strength and low-alloy Mg-1.8Li–2Sn–1Al (TLA221) and Mg-1.8Li–2Sn–2Al (TLA222) alloys were prepared, and the strengthening mechanism of TLA222 alloys was studied. TLA221 and TLA222 alloys were prepared by casting and extruded at a temperature of 523 °C with an extrusion ratio of 23:1. The microstructure and mechanical properties of TLA221 and TLA222 alloys were studied through OM, XRD, EBSD, and tensile tests. And the microstructure of TLA222 alloy was further studied using STEM. The results indicate that at room temperature, the yield strength (YS) of TLA221 alloy is 240 MPa, the ultimate tensile strength (UTS) is 284 MPa, and the elongation (EL) is 7.5 %. For TLA222 alloy, the corresponding values are 258 MPa, 309 MPa, and 7.1 %. The addition of Al element increases the alloy strength by approximately 20 MPa. Both TLA221 and TLA222 alloys are mainly composed of α-Mg phase, Mg 2 Sn and Li 2 MgSn compounds. The mechanical properties of TLA222 alloy are enhanced through mechanisms such as solid solution strengthening, fine - grain strengthening, second-phase precipitation strengthening, and dislocation strengthening. This research offers a theoretical support for the optimized design and application of Mg–Li alloys.