Abstract:The extrusion deformation behavior of Mg-3Bi and Mg-6Bi alloys at 400 ℃ and a strain rate of 0.001 s-1 was investigated, and the microstructure characteristics during extrusion were analyzed. Results show that as the Bi content increases from 3wt% to 6wt%, the plasticity of the alloy significantly improves, with the elongation increasing from 2.1% to 5.6%, and the tensile strength increasing from 188.2 MPa to 209.2 MPa. During high temperature extrusion deformation, the dominant softening mechanism of the Mg-3Bi alloy is discontinuous dynamic recrystallization (DDRX), whereas that of the Mg-6Bi alloy involves both DDRX and particle-stimulated nucleation (PSN). In this process, the grain size resulting from DDRX is larger than that produced by PSN. When Mg-Bi alloys are extruded through the die, the strain in the edge region of the die is significantly greater than that in the central region, consequently forming a deformation texture similar to that produced by equal-channel angular pressing (ECAP). Once the accumulated strain reaches a critical value, PSN is initiated. After extrusion deformation, the grains in both edge and central regions of the die exhibit a high degree of recrystallization, with their c-axes perpendicular to the extrusion direction, forming a typical extrusion fiber texture. The ranked contributions to the improvement of mechanical properties of Mg-Bi alloys, in descending order, are grain refinement, dislocation strengthening and nano-phase strengthening mechanisms. Compared with the Mg-3Bi alloy, the dimple density of Mg-6Bi alloy is higher, which disperses stress concentration and consequently enhances plasticity.