Enhancing the mechanical properties of Mg-7Li-3Zn-3Gd alloy by Extrusion-Swaging based on elemental segregation

AbstractA lightweight, high-strength, and ductile Mg-7Li-3Zn-3Gd alloy was fabricated through a two-stage mechanical processing route: initial hot-extrusion followed by room-temperature rotary swaging. The primary reinforcement mechanism of the test alloys had been investigated, with the following results. The yield strength, tensile strength and elongation of the Mg-7Li-3Zn-3Gd alloy at room temperature reach to 276 MPa, 303 MPa and 24%, respectively. The alloy mainly consisted of α-Mg, β-Li, Mg₃Zn₃Gd₂ and MgZn₂ phases. Dynamic precipitation and dynamic recrystallization occurred during hot extrusion. In the rotary-swaged alloy, precipitates dispersed and pinned the grain boundaries, refined the grains and hindered the dislocation movement. The Zn element segregated around Mg₃Zn₃Gd₂ and MgZn₂, stabilizing the interfaces and the intermetallic phases. The segregation of zinc further increased the radius of dislocation barriers, and improved performance. Notably, nanosized precipitates and element segregation synergistically regulated the mechanical properties of the Mg-7Li-3Zn-3Gd alloy.