Dynamic softening behavior and microstructural characterization of TiAl-based alloy during hot deformation

In the present study, the work-softening transient behavior of a powder metallurgy Ti-47A1-2Nb-2Cr alloy during hot deformation, along with microstructure characterization under a temperature of 950-1150 degrees C and a broad range of strain rates encompassing 0.001-0.1 s(-1), has been investigated. The single peak characteristic, which appeared in all the true stress-strain curves, indicates that DRX is a dominating softening mechanism. Furthermore, it was found that grain boundary bulging played a primary role in the DRX nucleation mechanism through observation of the microstructure evolution. The DRX critical strain occurs at epsilon(c) congruent to 0.73 epsilon(p), and the peak strain has been expressed through the Zener-Hollomon parameter. A mathematic model based on the Avrami equation has been established to describe the DRX behavior of the alloy, with the volume fractions of DRX grains calculated by the model in good agreement to that of the experimental results.