The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact...The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.展开更多
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 microstructur...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.展开更多
基金Project (51001014) supported by the Young Scientists Fund of the National Natural Science Foundation of China
文摘The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.
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)。
文摘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.
