TC4钛合金的高温变形行为及损伤机理研究

High temperature deformation behavior and damage mechanism of TC4 titanium alloy

本文在500~800℃、应变率为0.001~0.1 s^(-1)条件下对TC4钛合金进行高温力学性能测试,研究其高温变形行为。根据NCL损伤准则计算出临界损伤值,引入温度补偿因子Z,建立基于温度和应变率的损伤本构模型。通过表征显微组织,从微观上解释高温变形行为和损伤机理。结果表明:在500~800℃下,TC4钛合金的流变应力出现加工硬化,以及动态再结晶;用三次多项式对损伤本构模型进行拟合,拟合曲线和试验结果的相关系数达到0.96;由显微组织表征结果可得,在500~800℃下,TC4钛合金变形以动态再结晶为主。断裂方式为韧性断裂,且随温度的升高和应变率的降低,韧窝数量增多、形状更规则,材料塑性增强。

In this paper,high temperature mechanical properties of TC4 titanium alloy were tested at 500⁃800℃and strain rate was 0.001⁃0.1 s^(-1),and the high temperature deformation behavior was studied.The critical damage value was calculated according to the NCL damage criterion,and the temperature compensation factor Z was introduced to establish the damage constitutive model based on temperature and strain rate.By characterizing the microstructure,the high temperature deformation behavior and damage mechanism were explained microscopically.The results show that the flow stress of TC4 titanium alloy appears work hardening and dynamic recrystallization at 500⁃800℃.The damage constitutive model is fitted with cubic polynomial,and the correlation coefficient between the fitting curve and the test results reaches 0.96.According to the results of microstructure characterization,the deformation of TC4 titanium alloy is dominated by dynamic recrystallization at 500⁃800℃.The fracture mode is ductile fracture,and with the increase of temperature and the decrease of strain rate,the number of dimples increases,the shape becomes more regular,and the plasticity of the material increases.