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 °C. After hot-rolling, the β/γ lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average γ grain size of 10.5 μm. The dynamic recrystallization (DRX) of the γ phase was systematically investigated. A recrystallization fraction of 62.5% was obtained for the γ phase in the TiAl alloy sheet, when a threshold value of 0.8° 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: θ = 89° ± 3°<100>), which is associated with DDRX, occurs in both the recrystallized and deformed γ grains. The twin boundaries play an important role in the DDRX of the γ 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 °C, the alloy sheet exhibited excellent elongation (53%), corresponding to a failure strength of 467 MPa.