The evolution of long-period stacking ordered phase and its effect on dynamic recrystallization in Mg-Gd-Y-Zn-Zr alloy processed by repetitive upsetting-extrusion

Based on the repetitive upsetting-extrusion (RUE) process, the evolution of the LPSO phase and its effect on the dynamic recrystallization (DRX) of Mg-9Gd-4Y–2Zn-0.5Zr (wt%) alloy during the multi-pass deformation were studied. The results showed that with the increase of RUE processing, the DRX fraction gradually increased, the grains were effectively refined, and the texture was weakened. The lamellar LPSO phase mainly underwent mechanical crushing, bending, tearing, and kinking to become refinement. The block-shaped LPSO phases dissolved during the deformation process, forming a stripe-like structure, and its rest of the refinement mechanism was similar to the lamellar phase. The refinement of block-shaped phase was slower than that of lamellar phase. However, the block-shaped phases always promoted DRX through the PSN mechanism, while the lamellar phases with a large volume inhibited the generation of DRX. After the refinement of lamellar phases, the inhibition effect was transformed into the promotion effect, which leaded to a continuous increase in the DRX fraction. This further promoted the uniform distribution of the LPSO phases and obtained a more ideal microstructure.