Achieving high modulus and strength in ultra-light Mg-Li alloys through in situ-synthesized Mg2Si phase

• Mg-8Li-3Al-2Zn-1Y-0.5Mn-0.5Gd-1Si alloy offers outstanding mechanical properties. • Grain refinement and CTE mismatch strengthening mechanism significantly enhance strength. • Elastic modulus enhanced by solute atoms and the high-modulus Mg 2 Si phase formation. Enhancing the low modulus and absolute strength of Mg-Li alloys remains a key research focus. This study employed an in situ-synthesis strategy to incorporate high-modulus phases, such as Mg 2 Si, achieving a synergistic improvement in strength, plasticity, and modulus. The presence of Mg 2 Si improved the microstructure of the matrix and promoted dynamic recrystallization, leading to a refined grain size of 2.9 µm. Through the combined effects of grain refinement strengthening and coefficient of thermal expansion mismatch strengthening, the Mg-8Li-3Al-2Zn-1Y-0.5Mn-0.5Gd-1Si alloy exhibited exceptional mechanical properties, including a yield strength of 248 MPa, an ultimate tensile strength of 273 MPa, an elastic modulus of 51 GPa, and a plasticity of 20.6 %. This study offers a new approach for designing and developing ultra-light, high-modulus Mg-Li alloys.