The deformation and failure mechanisms of γ-TiAl alloy with pre-existing crack and twin boundary are investigated by using molecular dynamics simulation. The effects of the crack position on the deformation and failu...The deformation and failure mechanisms of γ-TiAl alloy with pre-existing crack and twin boundary are investigated by using molecular dynamics simulation. The effects of the crack position on the deformation and failure mechanisms of γ-TiAl specimen are analysed through the snapshots of crack propagation, microstructure of crack tip and stress-strain curves. The simulation results show that the dislocation motion is impeded, the good ductility can be maintained and the strength would be improved simultaneously by the twin boundary. The microstructure evolution of crack tip would change with crack positions. Essentially,the deformation behaviour mainly results from the reaction of dislocation-dislocation, dislocation-twin and twin-twin. Besides,the hierarchical twin is a main plastic deformation mechanism leading to strength of γ-TiAl specimen enhancement with noncompromising ductility and strain hardening. Based on stress-strain curves, it can be concluded that the yield strength varies with crack positions. They are the determinant factors for variation of the yield strength with different crack positions such as dislocation behaviour, stacking fault and hierarchical twin. The ductile-brittle transition associated with the dislocation motion and the decohesion failure of crack tip atom can be observed from the lower boundary crack and the center crack models. The crack propagation caused by the coalescent of the void and the crack tip is the main failure mechanism of γ-TiAl specimen. In addition, the results reveal that the mechanism of crack propagation would be influenced by pre-existing twin boundary which can prevent the crack propagation and improve the fracture toughness.展开更多
Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompressio...Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.展开更多
基金supported by the National Natural Science Fundation of China(Grant Nos.51665030,51865027)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT_15R30)the Doctoral Research Foundation of Lanzhou University of Technology
文摘The deformation and failure mechanisms of γ-TiAl alloy with pre-existing crack and twin boundary are investigated by using molecular dynamics simulation. The effects of the crack position on the deformation and failure mechanisms of γ-TiAl specimen are analysed through the snapshots of crack propagation, microstructure of crack tip and stress-strain curves. The simulation results show that the dislocation motion is impeded, the good ductility can be maintained and the strength would be improved simultaneously by the twin boundary. The microstructure evolution of crack tip would change with crack positions. Essentially,the deformation behaviour mainly results from the reaction of dislocation-dislocation, dislocation-twin and twin-twin. Besides,the hierarchical twin is a main plastic deformation mechanism leading to strength of γ-TiAl specimen enhancement with noncompromising ductility and strain hardening. Based on stress-strain curves, it can be concluded that the yield strength varies with crack positions. They are the determinant factors for variation of the yield strength with different crack positions such as dislocation behaviour, stacking fault and hierarchical twin. The ductile-brittle transition associated with the dislocation motion and the decohesion failure of crack tip atom can be observed from the lower boundary crack and the center crack models. The crack propagation caused by the coalescent of the void and the crack tip is the main failure mechanism of γ-TiAl specimen. In addition, the results reveal that the mechanism of crack propagation would be influenced by pre-existing twin boundary which can prevent the crack propagation and improve the fracture toughness.
基金the National Natural Science Foundation of China(Nos.51605212 and 51665028)the Natural Science Foundation of Gansu Province(No.17JR5RA122)
文摘Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.
