对Ti-23Al-17Nb合金在温度为940~1000 ℃, 恒应变速率为1.7×10^-3~5.5×10^-5 s^-1下的单向超塑拉伸变形行为进行了研究. 结果表明, 随着变形温度的升高, 延伸率先增加后减小, 在960 ℃, 5.5×10^-5 s^-1条件下获得最大延伸率为1447.5%. 低应变速率条件下, Nb含量的增加使合金的加工硬化阶段增加. 超塑变形有利于消除原始织构组织, 对比原始组织, 超塑拉伸过程中长条α₂相发生了球化, 并且其尺寸和含量随着温度升高逐渐减少, α₂和B2相比例为50∶50时可达到最佳变形. 利用Zener-Hollomn参数和Arrhenius方程建立了TAC-1B合金的峰值应力本构方程, 其变形激活能Q=390.76 kJ/mol, 为科学设计和有效控制Ti-23Al-17Nb合金的超塑成形工艺提供了理论依据.

Superplastic forming is one of effective method to solve the forming difficulty of Ti₃Al based alloy. In this work, the superplasticity of Ti-23Al-17Nb alloy sheet under the conditions of 940~1000 ℃ and 1.7×10^-3~5.5×10^-5 s^-1 are studied. The results show the elongation changes as a parabola with the deformation temperature increasing, and the maximum elongation obtained at 960 ℃ and 5.5×10^-5 s^-1 is 1447.5%. Deformation hardening period increases much more than soften period due to the increasing of element Nb under low strain rate. Compared with primary microstructure, the superplastic deformation could eliminate the texture, the lath-like α₂ grains gradually disappeared, the α₂ grains became more equiaxed, and the content and size of α₂ grains are decreasing with increasing of deformation temperature, the volume fraction of α₂ and B2 phase could reach the optimum deformation at 50∶50. A constitutive relationship based on the Zener-Hollomn parameter and Arrhenius equation was defined for the TAC-1B alloy, and the deformation activation energy Q=390.76 kJ/mol. The results could provide a theory basis for the design and control of TAC-1B alloy superplastic forming process.