摘要
The microstructure characteristics in early stage shear localization of near-αTi−6Al−2Zr−1Mo−1V titanium alloy were investigated by split Hopkinson pressure bar(SHPB)tests using hat-shaped specimens.The microstructural evolution and deformation mechanisms of hat-shaped specimens were revealed by electron backscattered diffraction(EBSD)method.It is found that the nucleation and expansion of adiabatic shear band(ASB)are affected by both geometric and structural factors.The increase of dislocation density,structure fragment and temperature rise in the deformation-affected regions provide basic microstructural conditions.In addition to the dislocation slips,the extension twins detected in shear region also play a critical role in microstructural fragmentation due to twin-boundaries effect.Interestingly,the sandwich structure imposes a crucial influence on ASB,which finally becomes a mature wide ASB in the dynamic deformation.However,due to much larger width,the sandwich structure in the middle of shear region is also possible to serve as favorable nucleation sites for crack initiation.
采用Hopkinson冲击实验装置(SHPB)研究近α型Ti−6Al−2Zr−1Mo−1V钛合金帽形试样剪切局部化的组织特征,通过背散射电子衍射技术(EBSD)揭示帽形试样的组织演变及剪切变形机制。结果表明,绝热剪切带的形核与扩展受几何因素及组织因素的影响。变形影响区中的位错增值、组织细化和温升提供基本的组织条件。除位错滑移外,在剪切区中还发现了大量的拉伸孪生,孪晶界大大加速了组织细化过程。三明治结构对绝热剪切带最终形态有很大影响,在动态变形过程中,这种结构会形成更宽、更稳定的绝热剪切带。但是,很宽的三明治结构也可能成为利于裂纹形核的位置。
基金
financial support from Pre-research Project of Equipment Development Department of China(No.41422010505)
the Technology Innovation Leading Program of Shanxi Province,China(No.2019CGHJ-21)。
