Abstract
The dynamic recrystallization (DRX) mechanism and microstructure evolution of the as-forged Ti-43Al-9V-Y-0.2Y alloy were investigated by plane strain compression tests under different deformation conditions. The results show that the strain rate has little influence on the microstructure components of present alloy, whereas a large amount of γ-phase undergoes γ→α₂-phase transformation with the total reduction from 40 to 60 % at a constant strain rate. Additionally, DRX and deformation twinning are the primary dynamic softening mechanisms of present alloy. The extent of DRX increases with the decreasing strain rate and increasing total reduction. Meanwhile, twin boundaries (TBs) are observed in γ-phase of all the samples, which provides coordinated deformation for non-uniform deformation of present alloys. The fraction of TBs reduces from 9.51 to 0.657 % with the increase of strain rate, and rises from 0.657 to 1.05 % with the increase of total reduction, testifying that TBs are connected with DRX nucleation. At the same time, the trend of pseudo twin boundaries (PTBs) content is similar to that of TBs, which is also related to the strain rate and total reduction. Besides, many fine DRX grains located around the TBs and PTBs further explain that the TBs and PTBs promote DRX nucleation. The fiber intensity peak value decreases, and the fiber distribution disperses in the pole figure of α₂-phase after DRX.

Key words
TiAl-based alloy, plane strain compression, microstructure characteristic, dynamic softening mechanism, phase transformation

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