Establishing a unified constitutive model to simulate the hot deformation behaviors, microstructure evolution and fracture behaviors under different stress states during the hot forming of titanium alloy is indispensable. The high temperature tensile tests were first carried out on different stress states of forged Ti-6Al-4 V alloy specimens to analyze the flow behaviors, microstructure evolution and fracture mechanism. The results show that the effect of temperature on fracture elongation is more significant than strain rate. High temperature and low strain rate will increase the dynamic recrystallization (DRX) volume fraction and softening effect, which inhibits the nucleation and growth of voids, thereby enhancing the plastic deformation ability of the alloy. The DRX volume fraction, grain size and stress triaxiality were introduced into the unified Gurson-Tvergaard-Needleman (GTN) damage model using the internal state variables. The parameters of GTN model were modified by the Response Surface Method (RSM) and compared with the high temperature tension. Finally, the established GTN damage model was successfully applied to finite element (FE) simulation under different stress states. The correlation coefficient R of predicted stress is 0.989, and the maximum errors of DRX volume fraction and grain size are 9.86% and 6.54%. The research results can provide a basis for the performance control in hot working of titanium alloy.

建立统一的本构模型来模拟钛合金热成形过程中不同应力状态下的热变形行为、显微组织演化和断裂行为是必不可少的。首先对锻造 Ti-6Al-4 V 合金试样进行不同应力状态下的高温拉伸试验，分析其流动行为、微观组织演变和断裂机制。结果表明，温度对断裂伸长率的影响比应变速率的影响更为显着。高温和低应变速率会增加动态再结晶（DRX）体积分数和软化效应，从而抑制空洞的形核和长大，从而增强合金的塑性变形能力。使用内部状态变量将 DRX 体积分数、晶粒尺寸和应力三轴度引入统一的 Gurson-Tvergaard-Needleman (GTN) 损伤模型中。采用响应面法(RSM)对GTN模型参数进行修正，并与高温拉伸情况进行比较。最后，所建立的GTN损伤模型成功应用于不同应力状态下的有限元（FE）仿真。预测应力的相关系数R为0.989，DRX体积分数和晶粒尺寸的最大误差分别为9.86%和6.54%。研究结果可为钛合金热加工性能控制提供依据。