Achieving strength-ductility-biodegradation synergy in a low-alloyed Mg-Sn-Li-Ca alloy via multi-polarization of texture and second phases

• Synergistic enhancement of strength, ductility, and corrosion resistance in Mg–Sn–Li–Ca alloys via multi-polarization. • Shear-induced C1 texture enables high ductility and low biodegradation via twinning and grain reorientation. • This study details a viable way to make high-performance biodegradable Mg alloy rods via microstructure and texture control. Wrought Mg-Sn alloys are promising for biomedical applications due to their excellent biocompatibility, biodegradability, low density, and high specific strength. However, the poor corrosion resistance and mechanical performance of conventional wrought Mg-Sn alloys limit their clinical applications in load-bearing components. To address these challenges, an extrusion-shearing (ES) process was applied to a novel low-alloyed Mg-Sn-Li-Ca alloy, tailoring its microstructure and texture for comparison with conventional extrusion (EX). The ES process resulted in a significantly refined and homogeneous microstructure, reducing the average grain size to 4.9 µm, less than half of the EX sample (11.1 µm). Instead of a typical single-pole texture component with //extrusion direction (ED) in EX sample, the ES sample showed a multipolar texture consisting of three fiber texture components: C1 (115°, 90°, 0∼60°), C2 (175°, 90°, 0∼60°), and P (150°, 0∼90°, 30°). The ES sample achieved a tensile yield strength of 231.8 MPa and elongation of 14.3%, representing improvements of 10.4% and 24.3% over the EX sample, respectively. Microstructural evolution combined with visco-plastic self-consistent modeling revealed that the C1 component promotes {10–12} twinning in the ES samples. The enhanced strength and ductility of the ES samples stemmed from multi-polarization of texture, second-phase distribution, and more homogeneous grain refinement. Moreover, corrosion behavior in α-minimum essential medium was investigated through immersion and electrochemical tests. Although both EX and ES samples exhibited similar high biocompatibility, the biodegradation rate of the ES samples was only 68.2% of the EX sample under immersion. In the ES sample, the multidirectional second-phase streamlines (i.e., multi-polarization of the second phase) inhibited pitting corrosion; the more corrosion-resistant {1–217} planes are nearer to the sample surface in grains with C1 texture component, replacing the {10–10} planes in the EX samples. These findings provide a viable strategy for advanced biodegradable implants via crystallographic engineering.