Investigation on low cycle fatigue behaviors of the [001] and [011] oriental single crystal superalloy at 760 ℃

摘要

Low cycle fatigue behaviors of a 3Re Ni-base single crystal superalloy with the [001] and [011] orientations have been investigated. At 760 °C, both the [001] and [011] specimens fracture along crystallographic planes. However, the results also indicate a large difference in fatigue deformation behaviors of these two oriented specimens, which is reflected in different deformation mechanisms. For the cyclic stability behavior of the [001] specimens, uneven cross-slip and tangled dislocations and continuous stacking faults cause local stress concentration in the matrix and have an influence on work hardening, while the stress concentration is reduced by dislocation pairs and stacking faults shearing γ′ phases. With respect to the [011] specimens, high density matrix dislocations, parallel dislocations and secondary cracks increase resistance to dislocation movement, resulting in cyclic hardening. We discovered continuous stacking faults that have been rarely reported in the low cycle fatigue. Also, these findings might bring about substantial insights that fatigue fracture and deformation mechanisms are responsible for low cycle fatigue anisotropy at intermediate temperature.