Inconsistent creep between dendrite core and interdendritic region under different degrees of elemental inhomogeneity in nickel-based single crystal superalloys

• 作者: Wanshun Xia Xinbao Zhao Liang Yue Quanzhao Yue Jiangwei Wang Qingqing Ding Hongbin Bei Ze Zhang
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2021,（33）
• 页码范围: 88-97
• 页数: 10页
• 语种: 英文

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 el-emental 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 in γ'phase,faster degradation of dislocation networks and facili-tated 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 in-consistency 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 re-duced 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.