The poor strength-ductility balance of Mg alloys at room temperature restricts their application and development. Texture engineering and grain boundary design are critical strategies for optimizing their mechanical properties. In this study, a high-strength-ductility binary Mg-7Sn alloy was fabricated through a composite processing route involving warm extrusion followed by room-temperature rolling. During the composite processing, a bimodal grain structure featuring dual-texture characteristics and a high proportion (38%) of low-angle grain boundaries (LAGBs) was formed in the alloy. The formation of a dual-texture microstructure, which consisted of C-texture (<0001>//RD) and basal texture, effectively weakened the intensity of the basal texture. Tensile test results indicated excellent strength-ductility balance, with yield strength, ultimate tensile strength, and elongation to failure being 235.6 MPa, 315.7 MPa, and 16.8%, respectively. The improvement in yield strength was primarily attributed to grain boundary strengthening, whereas the excellent ductility can be attributed to the enhanced crack initiation resistance and crack deflection enabled by the dual-texture structure, as well as the favorable local strain compatibility arising from the high volume fraction of LAGBs. This study provides valuable insights into the development of high-performance Mg alloys via texture engineering and grain boundary design.

The high-strength Mg-7Sn alloys (wt.%) with a heterogeneous grain structure were prepared by low-temperature extrusion (230 ℃) with the extrusion ratio of 9:1 (9E230) and 17:1 (17E230). The two extruded alloys contained fine dynamic recrystallization (DRX) grains (FG) and coarse unDRX grains (CG). The difference in deformability between CG and FG leads to the formation of heterogeneous grain structure. The average grain size and basal texture intensities increased while the volume fraction of CG decreased with increasing extrusion ratio. Tensile testing results indicated that the extruded 17E230 alloy exhibited higher tensile strengths than 9E230 alloy, whose tensile yield strength (σ_0.2), ultimate tensile strengths (σ_b), and elongation to failure (ε_f) were 231.1 MPa, 319.5MPa, and 12.54% respectively. The high tensile strengths of the extruded alloy mainly originated from grain refinement, texture strengthening, precipitation strengthening from a great number of nano-scale Mg₂Sn phases, solid solution strengthening and hetero-deformation induced (HDI) strengthening, while the good ductility of the alloy was also mainly attributed to grain refinement, activation of the non-basal slip systems and HDI hardening.