Microstructures and mechanical properties of as-extruded Mg–8Gd–2Y–1Zn–6Li alloy.

• A high-performance Mg-Li alloy with a TYS of 202 MPa is produced. • The studied alloy consists of deformed α-Mg grains and recrystallized β-Li grains. • Three Mg 3 RE variants form in the alloy and affect the mechanical properties differently. • A novel island-shape β 1R phase is firstly observed in the studied alloy. • The formation mechanism and strengthening mechanism of β 1R phase are clarified. In this study, a high-performance Mg–8Gd–2Y–1Zn–6Li (wt%) alloy having a TYS of 202 ± 2.6 MPa, UTS of 243 ± 2.1 MPa and EL of 10.7 ± 2.3% was successfully fabricated by casting, heat treatment and hot extrusion. The effects of intermetallic compounds on microstructure and mechanical properties were deeply investigated. The results show that the studied alloy consists of coarse deformed α-Mg grains with (0001) basal texture, fine recrystallized β-Li grains with (002) texture and three Mg 3 RE phase variants, which are bulk Mg 3 RE phase with a size range of 10–30 µm, spot Mg 3 RE phase with a size range of 1–2 µm and spherical Mg 3 RE phase with a size range of 0.3–1 µm, respectively. The spherical Mg 3 RE phase has a strong dispersion strengthening effect, while the bulk Mg 3 RE phase acts as crack resources and deteriorates the ductility. A novel island-like β 1 R phase (FCC, a = 0.78 nm) is found for the first time in the Mg-Gd-Li based alloys. It has a coherent (1 ̅ 12) β 1 R // (10 1 ̅ 0) α interface at the broad facet and a semi-coherent (1 ̅ 11) β 1 R // (11 2 ̅ 0) α interface at the end facet. The β 1 R phase transforms from β H phase at the semi-coherent interface by atomic shear of RE and Mg atoms. The β 1 R phase provides a significant precipitation strengthening effect to the studied alloy, while the dissolution of β 1 R phase results in the age-softening phenomenon. The high-performance of the studied alloy is mainly attributed to the α/β duplex structure, three Mg 3 RE phase variants, and β 1 R phase. [ABSTRACT FROM AUTHOR]