Effect of repetitive upsetting-extrusion on deformation uniformity and mechanical properties of Mg-Gd-Y-Zr alloy

Mg-8.3Gd-3.2Y-0.4Zr alloy underwent severe plastic deformation at 420 degrees C using 4-pass isothermal repetitive upsetting-extrusion (RUE) process. The deformation uniformity in different regions of the same sample after 4 passes of RUE was studied. The results showed that though there was slightly uneven deformation, the isothermal RUE process can improve uniformity. The strain in the central area is relatively small, and there are more deformed large grains. The dynamic recrystallization fraction at different positions is above 0.5, forming a more uniform microstructure, with the minimum average grain size being 10.66 mu m. Discontinuous dynamic recrystallization and continuous dynamic recrystallization occur at the same time, which promotes grain refinement and improvement of microstructure uniformity. Dynamic recrystallization weakens the texture, resulting the similar texture intensity of different positions of the sample. The bottom edge position with the most uniform microstructure obtained the best tensile properties, UTS reached 323 MPa.