RADIATION RESISTANT HIGH ENTROPY ALLOYS FOR FAST REACTOR CLADDING APPLICATIONS

高熵合金是近年来发展起来的一类新型材料，其中没有一种元素占主导地位。相反，四种或更多种元素以几乎相等的比例使用。据报道，这些合金具有广泛的有吸引力的特性，包括高温下的高强度、良好的耐腐蚀性和耐受辐射损伤的能力。这些特性使HEAs成为钠冷快堆燃料包壳的强有力的候选材料。这些反应堆可以在更高的温度下运行，使用更少的燃料，并且比目前的水冷和气冷反应堆更安全。然而，如果要在这种高度侵蚀性的环境中使用HEA，必须解决两个关键需求。首先是确定有前途的合金成分，制造它们并测试它们的机械性能。其次，需要了解导致优异的抗辐射损伤的机制。通过这一点，我们将建立辐射响应是否是普遍的所有HEAs和设计策略，以预测其他潜在的更好的系统进行调查。这项资助将使用离子辐照而不是中子，因为离子辐照更便宜，更快，可以更快地进行合金开发。将使用先进的显微镜方法研究辐照如何改变合金的结构，并将使用新的微观机械测试方法研究辐照对机械行为的影响。重要的是，这些方法可用于测量900 ℃以上温度下的机械性能，因此可在辐照和未辐照条件下研究工作温度下的机械性能。一旦最有前途的合金，具有最好的抗辐射损伤，已确定其耐液体钠腐蚀将进行研究。通过这种方法，我们将开发出一种新型的合金，可用于钠冷快堆燃料包壳。

High entropy alloys are a recently developed novel class of materials in which no one element dominates. Instead four or more elements are used in near equal proportions. These alloys have been reported to have a wide range of attractive properties including high strengths at high temperatures, good corrosion resistance and ability to withstand irradiation damage. These properties make HEAs strong candidate materials for use as fuel cladding in sodium cooled fast reactors. These reactors can operate at higher temperatures, using less fuel and are safer than current water and gas cooled reactors.However if HEAs are to be utilised in this highly aggressive environment there are two key needs that must be addressed. The first is to identify promising alloy compositions, manufacture them and characterise their mechanical behaviour. Secondly the mechanisms that lead to the excellent resistance to irradiation damage need to be understood. Through this we will establish whether the irradiation response is universal to all HEAs and devise strategies to predict other potentially better systems to investigate. This grant will use ion irradiations rather than neutrons as ion irradiations are cheaper and faster to carry out and allow for more rapid turn around in alloy development. How the structure of the alloys is changed by irradiation will be studied using advanced microscopy methods and the effect the irradiation has on the mechanical behaviour will be studied using novel micro-mechanical testing methods. Importantly these methods can be used to measure mechanical behaviour at temperatures over 900oC, so the mechanical properties at the operational temperature can be studied in both irradiated and unirradiated conditions. Once the most promising alloys, with the best resistance to irradiation damage, have been identified their resistance to liquid sodium corrosion will be studied. In this way we will develop a novel alloy which can be used as fuel cladding in sodium cooled fast reactors.