The in-situ TEM observation of nanocrack in titanium aluminide

• 作 者: 褚武杨 张跃 王燕斌 肖纪美
• 机 构: Department of Materials Physics, University of Science and Technology, Beijing 100083, Chinarrrr
• 出 处: Science in China,Ser.A
• 发表日期: 1995年02期
• 关键词: titanium tensile dislocation brittle continuously notch nucleation propagate emi

The results of tensile test in TEM for a brittle material, Ti-24Al-11Nb alloy, show that a lot of dislocations can also be emitted from a brittle crack tip and a dislocation-free zone (DFZ) is formed. The DFZ is an elastic zone with large strain and the stress in the DFZ may reach the cohesive strength of the material provided that the crack tip is sharp enough and the applied stress is large enough, resulting in initiating of a nanocrack in the DFZ or sometimes at the crack tip. The nanocrack formed in the DFZ is stable and will propagate into a deavage microcrack through multiplication and movement of dislocations in the plastic zone. Increasing the applied stress, the crack can stably propagate continuously or discontinuously.

The results of tensile test in TEM for a brittle material, Ti-24Al-11Nb alloy, show that a lot of dislocations can also be emitted from a brittle crack tip and a dislocation-free zone (DFZ) is formed. elastic zone with large strain and the stress in the DFZ may reach the cohesive strength of the material provided that the crack tip is sharp enough and the applied stress is large enough, resulting in initiating of a nanocrack in the DFZ or sometimes at the crack tip . The nanocrack formed in the DFZ is stable and will propagate into a deavage microcrack through multiplication and movement of dislocations in the plastic zone. Increasing the applied stress, the crack can stly propagate continuously or discontinuously.