Abstract The micromechanical deformation behaviour of the commercial Ni-base polycrystalline Ni-base superalloy GH4169 has been investigated in terms of the volume fraction and grain boundary distribution of the δ (Ni3Nb) phase. The main objective of this work was to gain an understanding about the mechanisms of deformation of the superalloy at the grain scale. To that purpose, experimental and microstructural observations are relied upon to construct realistic models of the polycrystalline superalloy microstructure using crystal plasticity concepts. It was found that a volume fraction of the grain boundary δ phase in excess of approximately 3.0% results in a weakening of the room temperature strength, and the detrimental effect increases with increasing the δ phase volume fraction. This study also revealed that the grain boundary δ phase, being stronger than the surrounding grains, impedes the transmission of plastic slip through the grain boundaries, thus enhancing the localisation of plastic slip within the grains. However, the strengthening effect associated with such slip blocking mechanism by the δ phase is considerably lower than the weakening of the deformation resistance of the grains due to the depletion of the meta-stable γ″ precipitates within the grains resulting from the stable δ phase formation.

中文翻译：

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δ相对热处理镍基高温合金微观塑性演化的影响

摘要 从δ (Ni3Nb) 相的体积分数和晶界分布方面研究了商用Ni 基多晶Ni 基高温合金GH4169 的微观机械变形行为。这项工作的主要目的是了解高温合金在晶粒尺度上的变形机制。为此，依靠实验和微观结构观察，使用晶体塑性概念构建多晶高温合金微观结构的真实模型。发现晶界δ相的体积分数超过约3.0％会导致室温强度减弱，并且随着δ相体积分数的增加不利影响增加。该研究还揭示了晶界δ相，比周围晶粒更强，阻碍塑性滑移通过晶界的传输，从而增强了塑性滑移在晶粒内的局部化。然而，δ相与这种滑移阻塞机制相关的强化效果远低于由于稳定的δ相形成导致晶粒内亚稳定γ″析出物的消耗而导致的晶粒变形抗力的减弱。 .