Ti600合金在(α+β)相区的热变形行为和本构模型

Hot Deformation Behavior and Constitutive Models of Ti600 Alloy in (α+β) Phase Region

摘要:

对具有片层状初始组织的Ti600合金的热变形行为进行了研究。变形温度范围为800~960 ℃，应变速率范围为10^-3~1 s^-1。随后提出了应变硬化指数（n）来表征流动软化和加工硬化之间的竞争。并且通过分析流变曲线和观察显微组织研究了该合金的软化行为。结果表明，变形参数对Ti600合金的流变行为有显著影响。当变形超过峰值应变之后，n值逐渐降低，动态软化过程开始占主导地位。微观组织分析表明：热变形过程中，α相的弯曲、破碎、动态回复和动态再结晶行为是造成Ti600合金软化的主要原因。最后基于实验数据，建立了3种本构模型，分别是应变补偿Arrhenius模型、Hensel-Spittel模型和修正的Arrhenius模型，来表征Ti600合金的流变行为。将3种模型预测的流变应力与实验结果进行比较，并计算其相关系数值和平均相对误差值来评估模型的准确性。3种模型的相关系数值分别为0.965、0.989和0.997，平均相对误差值分别为12.86%，9.74%和3.26%。这些结果表明，这3种模型都可以描述Ti600合金的流变行为，而修正的Arrhenius模型具有最高的预测精度。

Abstract:

The high-temperature deformation behavior of Ti600 alloy with a lamellar initial microstructure was investigated in the temperature range of 800~960 ℃ and the strain rate range of 10^-3~1 s^-1. Subsequently, the strain hardening exponent (n) was proposed to characterize the competition of flow softening and work hardening. The softening behavior of this alloy was also studied according to flow curve analysis and microstructure observation. The results indicate that deformation parameters have significant influences on the flow behavior of Ti600 alloy. The n-value gradually decreases after the peak strain, which indicates that the dynamic softening begins to take dominant. The dynamic softening behavior of Ti600 alloy mainly attributes to the bending, fragmentation, dynamic recovery and recrystallization of α phase during the high-temperature deformation according to the microstructure characterization. Based on experimental data, original strain-compensated Arrhenius, Hensel-Spittel and modified Arrhenius constitutive models are established to describe the deformation behavior of Ti600 alloy. The flow stresses predicted by three models are compared with experimental results, and the calculated correlation coefficients are 0.965, 0.989, and 0.997. Also, the values of average absolute relative error are 12.86%, 9.74%, and 3.26%. These results suggest that three models can descript the flow behavior of Ti600 alloy, and the modified Arrhenius model exhibits the highest prediction accuracy.