Nanostructured Tungsten Alloys for Nuclear Fusion

核聚变提供了大规模低碳能源的前景，而且没有长寿命的放射性废物。为克服重大技术挑战而进行的50多年的全球研究在ITER实验中达到高潮，该实验目前正在法国的卡达拉什建设，将于2025年完成。在这项研究中，50兆瓦的输入加热预计将从1.5亿摄氏度的等离子体中输出500兆瓦的聚变功率，持续时间长达1000秒，这将证明聚变发电的商业潜力。用于建造这种反应堆的材料暴露在温度、热流、等离子体烧蚀以及中子辐照等极端条件下。尽管用于保护反应堆物理部件和材料的聚变等离子体采用了高度复杂的磁约束。最能承受这种温度的等离子体材料是钨，它是熔点最高的金属。然而，钨表现出脆性到韧性的转变温度（DBTT），同时也受到辐照脆化的影响。在这个项目中，将根据两个微观结构设计概念开发性能更高的新型钨合金。首先，利用两相组织实现纳米级晶粒细化，提高延展性和断裂韧性。其次，利用纳米尺度的晶界和半相干界面作为辐射损伤的汇。这种微观结构已经在最近开发的使用β - β - fe的Ti 'bcc高温合金中得到了证明，这被认为是W-Ti- fe三元体系中W的可能。另一种方法是使用两相混相间隙，如在W-Cr中，甚至在难熔金属“高熵合金”（HEAs）中，如TaNbHfZr。该项目将生产新的两相钨“bcc高温合金”，表征其微观结构，评估其机械性能以及潜在的变形机制和辐照损伤性能。

Nuclear fusion offers the prospect of large-scale low carbon energy with no long-lived radioactive waste. Over 50 years of worldwide research to overcome the significant technological challenges is culminating in the ITER experiment, currently under construction in Cadarache, France to be completed by 2025. In this, 50 MW of input heating is anticipated to output 500 MW of fusion power from a 150 million degrees C plasma sustained for up to 1,000 seconds, which will demonstrate the commercial potential of fusion power. The materials used to construct such reactors are exposed to extreme conditions in terms of temperature, heat flow and plasma ablation as well as neutron irradiation. This is despite the highly sophisticated magnetic confinement of the fusion plasma used to shield the reactor's physical components and materials. The leading plasma facing material to withstand such temperatures is tungsten, the highest melting point metal. However, tungsten exhibits a brittle to ductile transition temperature (DBTT), and also suffers from irradiation embrittlement.In this project new tungsten alloys with increased performance will be developed following two microstructural design concepts. Firstly, utilising two-phase microstructure to enable nano-scale grain refinement to improve ductility and fracture toughness. Secondly, utilising nano-scale grain boundaries and semi-coherent interfaces to act as sinks for irradiation damage. Such microstructures have been demonstrated within recently developed Ti 'bcc superalloys' using beta-beta' TiFe, which are suggested to be possible for W within the W-Ti-Fe ternary system. An alternative route is to use a two-phase miscibility gap as in W-Cr or even within refractory metal 'high entropy alloys' (HEAs) such as TaNbHfZr. This project would produce new two-phase tungsten 'bcc superalloys', characterise their microstructures and evaluate their mechanical properties as well as underlying deformation mechanisms and irradiation damage performance.