The intermediate temperature brittleness (ITB), sudden fracture with insufficient plasticity in the range around 600–900 °C in precipitation strengthened polycrystalline alloys, plays a serious threat on the failure of structural hot components. To reveal the relationship between microstructure and ITB, a typical precipitation strengthened alloy GH4151 has been fabricated and processed in various routines, including single crystal (SX) growth and thermal-mechanical processing and their mechanical properties have been tensile tested. The SX GH4151 alloy fractures in a ductile manner with elongation to fracture (EF) exceeding 10 % at all test temperatures. In contrast, all polycrystalline alloys exhibit some degree of brittleness (EFs less than 5 %) at the temperature range of 700–900 °C. Microstructural characterization by using advanced microscopy techniques and a high temperature mechanical testing system in a transmission electron microscope, dynamically reveal the origin of the ITB in situ and find that the ITB is primarily caused by oxidation accelerated grain boundary fracture. Moreover, the microstructural effect, mainly γ′ volume fraction and grain size on the plasticity of precipitation strengthened alloys is established. Our findings might provide guidelines for overcoming ITB of precipitation strengthened polycrystalline alloys.

中文翻译：

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沉淀强化 Ni 基多晶合金在中间温度下的晶界脆性


沉淀强化多晶合金在 600-900 °C 左右的温度下脆性 （ITB） 即塑性不足的突然断裂，对结构热构件的失效构成严重威胁。为了揭示微观结构与 ITB 之间的关系，制备了一种典型的沉淀强化合金 GH4151，并进行了不同的加工，包括单晶 （SX） 生长和热机械加工，并对其机械性能进行了拉伸测试。SX GH4151 合金在所有测试温度下均以延展性方式断裂，断裂伸长率 （EF） 超过 10%。相比之下，所有多晶合金在 700-900 °C 的温度范围内都表现出一定程度的脆性（EF 小于 5%）。 利用先进的显微镜技术和透射电子显微镜中的高温力学测试系统进行微观结构表征，在原位动态揭示 ITB 的起源，发现 ITB 主要由氧化加速 GB 断裂引起。此外，建立了微观组织效应，主要是 γ' 体积分数和晶粒尺寸对沉淀强化合金塑性的影响。我们的研究结果可能为克服沉淀强化多晶合金的 ITB 提供指导。