TiAl合金在(α_2+γ)两相区的热成形能力及组织演变(英文)

Hot Workability and Microstructure Evolution of TiAl Alloy in (α_2 +γ) Dual-phase Field

为了利用现有的高温合金锻造设备实现TiAl合金的包套锻造，对Ti-43A1-4Nb-1Mo-0．1B合金在（a2＋y）两相区的热成形能力进行了研究。结果表明，当温度下降到（a2＋y）两相区时，合金的热成形能力明显下降，只能在1050℃以上温度以0．001s。的应变速率进行变形；当温度低于1050℃时，试样发生开裂；当温度升高或应变速率降低时，组织中形成更多的动态再结晶晶粒，裂纹消失。然而，当试样采用厚度为1．5mm的不锈钢进行包套后，合金的热成形能力大大改善，可以在1050～1150℃以0．1S。的应变速率进行均匀变形，该变形条件更加有利于充分利用当前的工业锻造设备。同未包套试样相比，在相同变形条件下，包套试样中的动态再结晶晶粒较少。

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-43A1-4Nb-lMo-0.1B （at%） was investigated in （a2＋y） 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 compressed with strain rate of 0.001 s^（-1） at 1050-1150 temperature increases and/or the strain rate decreases, decreases into （a2＋γ） dual-phase field. The samples can be soundly ℃ and cracks are formed when the temperature is 1000 ℃. As the 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℃ with strain rate of 0.1 sI, which is favorable to current industrial trials. By comparison, there are not cracks but fewer recrystallized grains when packed-compressed under the same conditions.