Finite element analysis of γ′-phase raft mechanism in Ni-based single crystal superalloy
(1.Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing100044, China
2.北京市北京交通大学工程力学研究所)
2.北京市北京交通大学工程力学研究所)
Abstract: The finite element method was applied to study the mechanics of rafting of γ′ precipitates in a single crystal Ni-based superalloy with the [001] orientation. The results show that the creep and rafting are closely related with the stress and strain energy density distributions in the matrix channels. The application of an external stress leads to differential levels of von Mises stress and strain energy density, and the largest value of the stress appears at the corners of the matrix near the interface. Creep dislocations penetrate preferentially into the most highly stressed matrix channels where the γ′-phase rafting is also enlarged. Meanwhile, the von Mises stress of γ matrix and γ′ precipitate increases with the increase of temperature, thus the rafting becomes easier at a higher temperature. Moreover, according to the analysis of slip systems for the Ni-based superalloy, the critical external load for bowing a dislocation through a matrix channel at 950 ℃ is about 180 MPa, which is consistent with the related experimental results.
Key words: Ni-based superalloy; rafting; creep dislocation; critical external load; finite element analysis