Abstract Functionally graded (FG) iron/tungsten (Fe/W) composites are considered for stress-relieving interlayers in tungsten-steel joints, required in future fusion reactors. The macroscopic gradation of the two materials allows relaxation of thermally-induced stresses and hence extend the lifetime of the cyclic-loaded dissimilar materials joints. While many properties, e.g. thermal expansion and strength, of the as-manufactured Fe/W composites are promising with respect to the anticipated application, the temperature-induced microstructural changes and their effect on the material properties remain largely unexplored. Given that the thermodynamic system of Fe W contains two types of intermetallic phases, understanding the microstructural changes in the FG Fe/W composites is crucial for long-term operation of fusion reactors. In the present work, the microstructure of ultra-fast sintered Fe/W composites containing 50 and 75 vol% tungsten is studied via electron microscopy (SEM) and X-ray diffraction (XRD) in as-manufactured and thermal aged conditions (300, 500, and 800 °C for up to 72 h). The hardness and modulus of selected composites are measured via nanoindentation, and the fracture toughness of the Fe W interfaces is tested via notched micro-cantilever bending tests. The results from microstructural and micromechanical analyses are discussed, and the materials are evaluated for their application in fusion reactors based on the microstructure-to-property relationship.

中文翻译：

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老化超快烧结功能梯度铁/钨复合材料的微观结构和微观力学评估

摘要 功能梯度 (FG) 铁/钨 (Fe/W) 复合材料被认为是未来聚变反应堆所需的钨钢接头中的应力消除夹层。两种材料的宏观渐变允许热应力松弛，从而延长循环加载的异种材料接头的寿命。虽然所制造的 Fe/W 复合材料的许多特性，例如热膨胀和强度，在预期应用方面很有前景，但温度引起的微观结构变化及其对材料特性的影响在很大程度上仍未得到探索。鉴于 Fe W 的热力学系统包含两种类型的金属间相，了解 FG Fe/W 复合材料的微观结构变化对于聚变反应堆的长期运行至关重要。在目前的工作中，通过电子显微镜 (SEM) 和 X 射线衍射 (XRD) 在制造状态和热时效条件下（300、500 和 800°）研究了含有 50 和 75 vol% 钨的超快烧结 Fe/W 复合材料的微观结构C 长达 72 小时）。通过纳米压痕测量所选复合材料的硬度和模量，通过缺口微悬臂梁弯曲试验测试 Fe W 界面的断裂韧性。讨论了微观结构和微观力学分析的结果，并根据微观结构与性能的关系评估了材料在聚变反应堆中的应用。和 800 °C 长达 72 小时）。通过纳米压痕测量所选复合材料的硬度和模量，通过缺口微悬臂梁弯曲试验测试 Fe W 界面的断裂韧性。讨论了微观结构和微观力学分析的结果，并根据微观结构与性能的关系评估了材料在聚变反应堆中的应用。和 800 °C 长达 72 小时）。通过纳米压痕测量所选复合材料的硬度和模量，通过缺口微悬臂梁弯曲试验测试 Fe W 界面的断裂韧性。讨论了微观结构和微观力学分析的结果，并根据微观结构与性能的关系评估了材料在聚变反应堆中的应用。