Hot workability and microstructure evolution of TiAl alloy in (α₂+γ) dual-phase field

To explore the possibility of near conventional forging of TNM alloys using existing equipment for superalloy, the hot workability of a typical TNM alloy with normal composition of Ti-43Al-4Nb-1Mo-0.1B (at%) was investigated in (α₂+γ) dual-phase field. Based on the hot workability maps and microstructure observation, it is found that the hot deformability of this alloy is dropped remarkably when the temperature decreases into (α₂+γ) dual-phase field. The samples can be soundly compressed with strain rate of 0.001 s^-1 at 1050~1150°C and cracks are formed when the temperature is 1000°C. As the temperature increases and/or the strain rate decreases, cracks vanish and more dynamic recrystallized grains are formed. Furthermore, its workability can be promoted when it is packed with 304 stainless steel with a thickness of 1.5 mm and the billets can be adequately deformed at 1050~1150°C with strain rate of 0.1 s^-1, which is favorable to current industrial trials. By comparison, there are not cracks but fewer recrystallized grains when packed-compressed under the same conditions.