Abstract
In order to break through the application bottleneck of insufficient creep resistance for TiAl alloy, twin strengthening strategy was introduced into TiAl alloy in this study. The results revealed that the hybrid precipitates (Ti2AlC and Y2O3) are capable of inducing heterogeneous nucleation of high-density nanotwins by applying long-term annealing treatment. Fundamentally, the formation of nanotwins is related to stacking faults, whose generation results from the movement of partial dislocations. The creep test results at 800 °C under 300 MPa showed that creep resistance of TiAl alloy was significantly enhanced with a life increase of 423.7%. Detailed TEM and HRTEM characterizations confirmed that profuse deformation twins and twin intersections can generate dynamically during creep. The twin boundary can act as a strong barrier to dislocation movement and the formation of twin intersection significantly shortens the mean free path for dislocation movement, which is contributed to the improvement in creep resistance. In addition, geometric phase analysis (GPA) indicated that the local strain at twin boundary and twin intersection is greatly increased after creep. These findings provide us with new ideas for enhancing creep resistance of TiAl alloys.
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