摘要
The creep inconsistency between dendrite core and interdendritic region is investigated in a nickel-based single crystal superalloy under 1373 K and 137 MPa.Two specimens with higher and lower degree of elemental inhomogeneity on dendritic structures are compared.For specimen with higher inhomogeneity,stronger segregation of refractory elements reinforces the local strength in dendrite core,but damages the strength in interdendritic region.Creep strain is accumulated faster in interdendritic region giving rise to promoted dislocation shearing inγphase,faster degradation of dislocation networks and facilitated topological inversion of rated structures.Although the segregation of refractory elements produces a high density of topologically close-packed(TCP)phase in dendrite core,faster accumulation of creep strain forms microcracks prior in interdendritic region that gives rise to final rupture of the specimen.In another specimen,increased solid solution time gives rise to overall reduced inhomogeneity.Creep inconsistency is relieved to show more uniform evolution of dislocation substructures and rafting between dendrite core and interdendritic region.The second specimen is ruptured by formation and extension of microcracks along TCP phase although the precipitation of TCP phase is relatively restricted under reduced inhomogeneity.Importantly,the balance of local strength between dendrite core and interdendritic region results in over 40%increase of creep rupture life of the second specimen.
基金
jointly supported by the National Natural Science Foundation of China(91960201,51988101)
the Key Basic Research Program of Zhejiang Province(2020C01002)
the Zhejiang Provincial Natural Science Foundation of China(LY20E010004)
the Fundamental Research Funds for the Central Universities(2019QNA4012)
the Innovation Fund of the Zhejiang Kechuang New Materials Research Institute(ZKN-18-Z01)
the supports of equipment and guidance of experiments of researchers in Centre of Electron of Microscopy of Zhejiang University。
