The influence of radial strain gradient on the mechanical properties and corrosion resistance of Mg-Zn-Zr-Nd alloy processed by cold rotary swaging

Due to the radial strain gradient induced during rotary swaging deformation of magnesium alloys, the microstructures at the center and edge typically exhibit distinct characteristics. Most studies have focused on the overall mechanical properties of magnesium alloys, yet they fail to address the performance discrepancies between edge and core regions, particularly with respect to achieving an optimal balance between mechanical performance and corrosion resistance. In this study, cold rotary swaging was performed on extruded Mg-Zn-Zr-Nd alloys at room temperature, resulting in rods exhibiting excellent comprehensive properties: high strength, moderate ductility, and corrosion resistance comparable to that of the as-extruded state. The results show that with progressive accumulation of rotary swaging strain, grains are progressively refined to the nanoscale, and the reduction in strain gradient leads to a diminished microstructural heterogeneity between the radial edge and core. The multi-directional shear deformation inherent in rotary swaging significantly reduces the size of second-phase particles. Following cold rotary swaging, the tensile strength and yield strength of the alloy increased from 302 MPa and 287 MPa to 381 MPa and 369 MPa, primarily attributed to grain boundary strengthening and dislocation hardening. A moderate elongation of 12.3% was concurrently retained. The corrosion rate (0.23 mm/y) remained close to that of the as-extruded alloy (0.19 mm/y). The improvement in corrosion resistance is attributed to the synergistic effects of grain refinement, second-phase particle refinement, and the development of a strong basal texture induced by rotary swaging.