Cavitation and failure during hot forging of Ti-6Al-4V
Cavitation and failure during hot forging of Ti-6Al-4V
复制标题
DOI：
10.1007/s11661-999-0289-0
复制
发表时间：
1999-05
期刊：
影响因子：
--
通讯作者：
S. Semiatin;R. Goetz;V. Seetharaman;E. Shell;A. Ghosh
中科院分区：
文献类型：
--
作者：
S. Semiatin;R. Goetz;V. Seetharaman;E. Shell;A. Ghosh
在Ti-6Al-4V的亚转变热饼锻造过程中，确定了具有转变的β（群体）显微组织的空穴萌生和总的自由表面断裂的发生。空穴引发机制是两种不同类型之一。在比β转变温度（Tβ）低约75 °C或更低的温度下，在位于晶界α相和层状集落之间的β相中的相对低的应变下发生空穴引发。相反，在接近相变的温度下（即，T <$Tβ−25 °C）时，由于部分到完全球化的α相的微断裂，在大得多的应变下发生空穴萌生。饼形锻造过程的有限元法（FEM）建模显示，二次拉伸应力已开发的区域，表现出空穴/断裂。有限元分析用于将空腔萌生和总自由表面断裂结果与之前单轴热拉伸试验的观察结果关联起来，其中观察到了相同的损伤机制。Cockcroft和莱瑟姆（C+L）的拉伸功准则给出了锻造和单轴拉伸行为之间的适度良好（定量）相关性。基于Rice和Tracey空穴增长模型的另一种比较给出了自由表面断裂的合理预测，但往往高估了次表面空穴萌生的发生率。
The occurrence of cavity initiation and gross, free-surface fracture during subtransus hot pancake forging of Ti-6Al-4V with a transformed beta (colony) microstructure was established. Cavity initiation mechanisms were one of two distinct types. At temperatures approximately 75 °C or more below the beta transus temperature (Tβ), cavity initiation occurred at relatively low strains in the beta phase lying between the grain-boundary alpha phase and the lamellar colonies. By contrast, at temperatures near the transus (i.e., T≈Tβ−25 °C), cavity initiation occurred at much larger strains as a result of microfracture of partially-to-fully globularized alpha phase. Finite element method (FEM) modeling of the pancake forging process revealed that secondary tensile stresses had been developed in the regions that had exhibited cavitation/fracture. The FEM analyses were used to correlate both the cavity initiation and the gross free-surface fracture results to previous observations from uniaxial hot tension tests in which identical damage mechanisms had been observed. The tensile work criterion of Cockcroft and Latham (C+L) gave moderately good (quantitative) correlation between the forging and uniaxial tension behaviors. An alternate comparison based on the Rice and Tracey cavity growth model gave reasonable predictions of free-surface fracture but tended to overestimate the incidence of subsurface cavity initiation.