Influence of extrusion ratios on the microstructure, mechanical properties, and biocorrosion behavior of Mg-1.0Zn-0.3Zr-1.5Er alloy

Effects of extrusion ratio on the microstructure, mechanical properties, and biocorrosion behavior of Mg-1.0Zn-0.3Zr-1.5Er alloy are investigated. Following extrusion, fine Mg 3 Er 2 Zn 3 , MgEr, and minor Zn 2 Zr 3 phases are distributed in stripes along the extrusion direction. In samples with low extrusion ratio, deformation is governed by basal and prismatic slips, resulting in a bimodal grain structure characterized by an intense basal texture. As the extrusion ratio increases, the basal texture is progressively weakened, facilitating the development of a homogeneous grain structure. Concurrently, the average grain size exhibits a slight increase with higher extrusion ratios. When the extrusion ratio is increased from 6 to 12, the ultimate tensile strength and yield strength decrease by 24% and 30%, respectively, while the elongation increases by 36%. The reduction in tensile strength is attributed to the synergistic effects of the gradual disappearance of bimodal grain structure, a decrease in the density of geometrically necessary dislocations, a reduction in the volume and size of second phases, and the gradual growth in grain size. The enhanced elongation is ascribed to a higher recrystallization degree, more uniform grain distribution, and lower dislocation density. Additionally, the corrosion rate in simulated bodily fluids initially decreases and then increases with increasing extrusion ratio. The sample with an extrusion ratio of 10 exhibits the lowest corrosion rate. The improved corrosion resistance is associated with a denser oxide film, an elevated corrosion potential, a lower dislocation density, and the dispersion distribution of second phases. • Extrusion ratio increases from 6 to 12, UTS and YS decrease, while EL increases. • Strengthening contribution: grain size > texture > work hardening > second phases. • Er restrains dynamic recrystallization, leading to a bimodal grain structure. • Proportion of basal plane increases with the increase of extrusion ratio. • ER10 sample exhibits superior mechanical properties and biocorrosion resistance.