Dynamic Recrystallization of the Constituent γ Phase and Mechanical Properties of Ti-43Al-9V-0.2Y Alloy Sheet

A crack-free Ti-43Al-9V-0.2Y alloy sheet was successfully fabricated via hot-pack rolling at 1200 degrees C. After hot-rolling, the beta/gamma lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average gamma grain size of 10.5 mu m. The dynamic recrystallization (DRX) of the gamma phase was systematically investigated. A recrystallization fraction of 62.5% was obtained for the gamma phase in the TiAl alloy sheet, when a threshold value of 0.8 degrees was applied to the distribution of grain orientation spread (GOS) values. The high strain rate and high stress associated with hot-rolling are conducive for discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), respectively. A certain high-angle boundary (HAGB: theta = 89 degrees +/- 3 degrees <100>), which is associated with DDRX, occurs in both the recrystallized and deformed gamma grains. The twin boundaries play an important role in the DDRX of the gamma phase. Additionally, the sub-structures and sub-boundaries originating from low-angle boundaries in the deformed grains also indicate that CDRX occurs. The mechanical properties of the alloy sheet were determined at both room and elevated temperatures. At 750 degrees C, the alloy sheet exhibited excellent elongation (53%), corresponding to a failure strength of 467 MPa.