Role of stress on creep behaviors of MarM247LC directional-solidified superalloy was investigated at 900°C under different stresses. With reduced stress from 400 MPa to 230 MPa, the creep life has increased by a factor of 24, from 54 h to 1351 h. Apart from that, the deformation mechanism, creep curves, and fracture behavior of the alloy also presented strong dependence on stress. It found that the main deformation mechanism was the precipitate shearing by a/2<110> dislocations under 400 MPa. In contrast, dislocations bypassing γ′ by a glide-climb process dominated the steady-state creep under 230 MPa. Moreover, the degradation of γ/γ′ microstructure and formation of creep pores have accelerated the onset of tertiary creep and resulted in more ductile fracture modes at low stress regime.

中文翻译：

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应力对 MarM247LC DS 高温合金蠕变行为的作用

研究了 900°C 不同应力下应力对 MarM247LC 定向凝固高温合金蠕变行为的影响。随着应力从 400 MPa 降低到 230 MPa，蠕变寿命增加了 24 倍，从 54 小时增加到 1351 小时。除此之外，合金的变形机制、蠕变曲线和断裂行为也表现出强烈的应力依赖性。结果发现，主要变形机制是 400 MPa 下 a/2<110> 位错的析出物剪切。相比之下，在 230 MPa 下，通过滑移-攀爬过程绕过 γ' 的位错主导了稳态蠕变。此外，γ/γ'微观结构的退化和蠕变孔隙的形成加速了三次蠕变的发生，并导致低应力状态下更多的韧性断裂模式。