Hot Tensile Deformation Mechanism and Dynamic Softening Behavior of Ti-6Al-4V Alloy with Thick Lamellar Microstructures
Hot Tensile Deformation Mechanism and Dynamic Softening Behavior of Ti-6Al-4V Alloy with Thick Lamellar Microstructures
复制标题
厚片状Ti-6Al-4V合金热拉伸变形机制及动态软化行为
DOI：
10.1002/adem.201901193
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发表时间：
2019-12-17
影响因子：
3.6
通讯作者：
He, Dao-Guang
中科院分区：
文献类型：
--
作者：
Lin, Y. C.;Wu, Qiao;He, Dao-Guang
通过单轴热拉伸试验研究了一种具有厚片层组织的Ti-6Al-4V合金的变形机制和动态软化行为。真应力首先由于位错的快速扩散和缠结而迅速达到峰值，然后随着变形量的增加，由于动态软化而逐渐减小。动态软化行为主要是由片状α相的严重动态球化引起的。α相的球化过程总是伴随着大角度晶界的形成。随着变形温度的升高，球化α相的比例增加。断裂机制是微孔聚结，即，在拉伸变形的初始阶段，微孔开始出现。随着变形量的增加，微孔洞数量增加，微孔洞不断累积并加速扩展，直至最终断裂。根据实验测得的流变应力曲线，建立了修正的Arrhenius型方程和Hensel-Spittel（HS）模型。所建立的应变补偿Arabidius型（SCAT）和HS模型的平均绝对相对误差分别为6.108%和3.385%。两种模型均能较好地描述厚片层组织Ti-6Al-4V合金的热拉伸流变特性。
The deformation mechanisms and dynamic softening behavior of a Ti-6Al-4V alloy with thick lamellar microstructures are studied by uniaxial hot tensile tests. The true stress first rapidly reaches a peak value because of the rapid dislocations proliferation and tangle, and then gradually decreases due to the dynamic softening with raising the deformation amount. The dynamic softening behavior is mainly induced by the severe dynamic globularization of lamellar alpha phases. The globularization of alpha phase is always accompanied by the formation of high-angle grain boundaries (HAGBs). The fraction of globularized alpha phases increases with the increasing deformation temperature. The fracture mechanism is microvoid coalescence, i.e., in the initial stage of tensile deformation, the microvoids begin to emerge. With the increasing deformation amount, the number of microvoids increases, and the microvoids accumulate and accelerate to propagate until the final fracture. According to the experimental flow stress curves, a modified Arrhenius-type equation and a Hensel-Spittel (HS) model are developed to forecast the flow stresses. The average absolute relative error of the established strain-compensated Arrhenius-type (SCAT) and HS models are 6.108% and 3.385%, respectively. Both models can be well used to describe the hot tensile flow characteristics of the Ti-6Al-4V alloy with thick lamellar microstructures.