Precipitate characteristics and their effects on the mechanical properties of as-extruded Mg-Gd-Li-Y-Zn alloy.

[Display omitted] • The TYS of the studied alloy is 295 MPa at 25℃ and 143 MPa at 200℃. • Theβ 1R phase is introduced in the studied alloy for the first time. • Theβ 1R phase forms by dislocation-assisted dynamic precipitation in hot extrusion. • Theβ 1R phase provides the alloy with a strong Orowan strengthening effect. In this work, a high-performance Mg-8.4Gd-4.4Li-3.5Y-1.4Zn (wt%) alloy was successfully prepared by low-temperature hot extrusion. The studied alloy has a TYS of 295 ± 1 MPa and an EL of 2.5 %±0.2 % at room temperature, 159 ± 8 MPa and 15.9 %±1.4 % at 150 °C, and 143 ± 4 MPa and 19.8 %±1.8 % at 200 °C. The high performance at temperatures up to 200 °C is attributed to the dispersion strengthening of three Mg 3 RE phase variants, the solid solution strengthening of alloying elements and the bimodal structure consisting of fine DRXed grains with random texture and coarse un-DRXed grains with basal texture. A novel island shaped β 1 R phase (FCC, a = 0.78 nm) with a size of 30 nm–100 nm is observed in the studied alloy. The β 1 R phase precipitates on the { 1 1 ¯ 00 } α prismatic planes. The strain-induced, dislocation-assisted dynamic precipitation during low-temperature hot extrusion is responsible for the formation of the β 1 R phase. The growth of the β 1 R phase is owing to the aid of the formation and transformation of zig-zag structures. The basal slip of < a > dislocations is the dominate deformation mechanism of the studied alloy in the early stage of tensile deformation at room temperature, while non-basal slip of < a > and < c + a > dislocations at 200 °C. Due to the strong interaction between β 1 R precipitates and dislocations, the densely distributed β 1 R precipitates significantly improve the mechanical properties via the Orowan strengthening both at room temperature and elevated temperatures. [ABSTRACT FROM AUTHOR]