Ti-7333合金β锻动态再结晶行为

 利用Gleeble3800热模拟试验机研究了在温度870～970℃和应变速率0.001～10s^-1范围内,近β钛合金Ti-7333 β锻热变形的组织演化规律及动态再结晶行为.实验结果表明,Ti-7333钛合金在温度较高、应变速率较低的情况下变形时,表现出典型的动态再结晶行为,动态再结晶晶粒尺寸和再结晶体积分数均随变形温度升高和变形速率降低而增大,而应变速率对再结晶晶粒尺寸的影响较显著.在变形速率较高(>0.1s^-1)且变形温度较低(<870℃)时,晶粒严重变形拉长,但动态再结晶将很难发生.因子Z决定着动态再结晶晶粒尺寸,二者之间为幂指数关系.通过回归分析方法得出动态再结晶晶粒尺寸的数学表达式为：lnD_r=8.50949-0.31411lnZ.采用该表达式可以对一定变形条件的动态再结晶晶粒尺寸进行精确预测,从而为Ti-7333钛合金热变形条件下的组织控制提供可靠依据.不适当的热变形工艺会造成组织粗大或者不均匀,进而使材料性能恶化.因此,应该从材料组织均匀性和晶粒细化角度选择最佳的热变形参数.

Dynamic Recrystallization Behavior of Ti-7333 Alloy in the β Hot Process

The effects of processing parameters on deformation microstructure evolution and dynamic recrystallization behavior of a new near β titanium alloy were investigated by using the Gleeble-3800 thermal and mechanical simulator in the temperature range of 870-970℃ and strain rate range of 10^-3-10s^-1. The results indicate that Ti-7333 alloy exhibits a typical DRX behavior at higher deformation temperature with lower strain rates. The recrystallization grain size and recrystallization volume fraction are also increase with the increase of deformation temperature and the decrease of strain rates. And strain rate affects the recrystallization grain size significantly. The grains are seriously deformed and elongated with higher strain rate (>0.1s^-1) and lower temperature (<870℃), however dynamic recrystallization will hardly occur. The recrystallization grain size is determined by Zener-Hollomon parameter Z, and an exponential function relation is held between D_r and Z. The model of dynamic recrystallization grain size is established by regression analysis method, that is, lnD_r=8.50949-0.31411lnZ. It is able to accurately predict the grain size of dynamic recrystallization under a certain deformation condition and lay a scientific foundation for microstructure controlling during hot deformation. Inappropriate thermal deformation process could cause coarse or non-uniform materials microstructure, thus deteriorating the performance. Thereby, the best hot deformation parameters must be selected from the perspective of microstructure uniformity and grain refinement.