采用Deform－3D有限元软件模拟了β－γ高Nb－TiAl合金Ti－45Al－8.5Nb－0.2W－0.2B－0.02Y(原子分数, %)的准等温锻造过程,分析了合金内部等效应力场、等效应变场、温度场的分布以及结合热压缩实验确定了该合金在特定工艺参数下的临界损伤因子.结果表明, 随应变速率的增大, 锻件的温度损失不明显, 等效应力增大,最大等效应变值增加, 变形均匀性系数下降, 工件变形更加均匀.结合模拟和实验结果, 确定了β－γ高Nb－TiAl合金在1150℃,应变速率5×10^-2 s^-1条件下进行包套准等温锻造过程中的临界损伤因子为0.206.

TiAl－based alloys containing high content of Nb are significantly promising for high-temperature structural applications in aerospace and automotive industries, due to their low density, excellent high temperature strength, high resistance to oxidization and creep resistance. However, poor hot workability limits their extensive applications. Owing to sufficient number of independent slip system, small deformation resistance, apt to plastic forming of disordered bccβ phase at elevated temperature, the novel β－γ TiAl with high content of Nb alloys exhibit excellent hot deformability. The quasi isothermal forging process of Ti－45Al－8.5Nb－0.2W－0.2B－0.02Y alloy is investigated by using a Deform－3D software. The effective stress, effective strain, temperature distribution of the alloy are analyzed. In order to obtain the critical damage factor of the alloy under the condition of 1150℃ and strain rate 5×10^-2s^-1, the hot compression physical simulation experiment of the alloy is performed to achieve true stress－strain data. By inputting these data into the Deform－3D software to simulate the true compression process, the critical damage factor is obtained. The results demonstrate that with increase of strain rate, the temperature loss becomes less obvious, the effective stress and the maximum effective strain rises up, the deformation uniformity ratio decreases and the deformation becomes more uniform. Combined with the simulation and experiment results, the critical damage factor of the β－γ TiAl alloy containing high content of Nb is 0.206 during the quasi isothermal forging process at\linebreak 1150℃ and strain rate 5×10^-2s^-1.