Recrystallization and mechanical properties of WE43 magnesium alloy processed via cyclic expansion extrusion

In this study, cyclic expansion extrusion (CEE), as a relatively new severe plastic deformation (SPD) process, is applied to a rare earth (RE) containing Mg alloy WE43. The effects of the processing temperature and the number of passes are also investigated. The results showed that dynamic recrystallization (DRX) occurred after CEE processing at 400℃, and a bimodal structure with ultrafine DRXed grains surrounded the unrecrystallized grains. However, the DRX at 330℃ was retarded because of the existence of RE elements. The tensile tests showed that a simultaneous increase in the strength and the ductility of WE43 is obtained after CEE processing at 400℃ via two passes. Furthermore, the highest ultimate tensile strength of 440 MPa was achieved after the second pass of CEE at 330℃, and the highest ductility of 21% was attained after the second pass of CEE at 400℃. The microhardness measurements showed that the hardness increased from HV 80 to HV 114 and HV 98 after two passes of CEE processing at 330 and 400℃, respectively. In conclusion, increasing the processing passes could increase the mechanical properties and the volume fraction of the recrystallized grains. Moreover, increasing the temperature reduced the strength and the microhardness even if the elongation increased.