Twin boundary fatigue crack nucleation in a polycrystalline Nickel superalloy containing non-metallic inclusions
Twin boundary fatigue crack nucleation in a polycrystalline Nickel superalloy containing non-metallic inclusions
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DOI：
10.1016/j.jmps.2022.104785
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发表时间：
2022-01-19
影响因子：
5.3
通讯作者：
Dunne, Fionn P. E.
中科院分区：
文献类型：
--
作者：
Bergsmo, Alexander;Xu, Yilun;Dunne, Fionn P. E.
非金属夹杂物和孪晶界是多晶镍基高温合金疲劳裂纹的优先形核部位。一个Heaviside HR-DIC，EBSD和多尺度建模策略（CPFE-DDP）被用来评估在RR 1000在高温下聚集的夹杂物附近的疲劳裂纹成核的实验观察。在第一次加载循环内观察到夹杂物断裂和脱粘。非金属夹杂物处的疲劳裂纹形核与相邻的含有孪晶界的粗晶中的疲劳裂纹形核一致。DDP模型的孪晶边界表明，建立滑动激活平行以及倾斜的接口，在DIC表征观察。DDP结果表明，堆积驱动在界面处产生局部GND密度，进而驱动高的局部储能密度和疲劳裂纹成核。这些条件被证明是由于各向异性的弹性约束在孪晶界。此外，由团聚体产生的复杂应力场驱动孪晶界附近的塑性，为疲劳裂纹形核提供了必要条件。
Non-metallic inclusions and twin boundaries are preferred fatigue crack nucleation locations in polycrystalline Ni-based superalloys. A Heaviside HR-DIC, EBSD and multi-scale modelling strategy (CPFE-DDP) was used to assess experimental observations of fatigue crack nucleation near agglomerated inclusions in RR1000 at elevated temperature. Inclusion fracture and deco-hesion were observed within the first cycle of loading. Fatigue crack nucleation at the non-metallic inclusion coincided with that in an adjacent coarse grain containing a twin boundary. DDP modelling of the twin boundary showed the establishment of slip activation parallel as well as oblique to the interface, as observed in DIC characterisation. The DDP results showed pile-up driven generation of local GND density at the interface, in turn driving high local stored energy density and fatigue crack nucleation. These conditions were shown to result from the anisotropic elastic constraint at the twin boundary. In addition, the complex stress field arising from the agglomerate drives plasticity near the twin boundary contributing to the necessary conditions for fatigue crack nucleation.