Cyclic deformation mechanism of a high-Nb TiAl alloy at high temperature

Tension and cyclic deformation tests of a nearly lamellar Ti-45Al-8Nb-0.2W-0.2B-0.1Y alloy were carried out at 750℃, and the corresponding microstructures were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the cyclic stress-strain curve of the alloy at 750℃ is above the static tensile curve, indicating an obvious cyclic hardening characteristic of the alloy at 750℃;the cyclic stress-strain behavior of the alloy is characterized by first hardening and then stabilization. TEM observations show that there are lots of dislocation pile-ups, pinnings and tanglings in cyclic deformation and tensile specimens, but large amounts of mechanical twinnings only occur in the former, implying that twinnings play a considerable role in the cyclic deformation process of the alloy at 750℃.