RADIATION RESISTANT HIGH ENTROPY ALLOYS FOR FAST REACTOR CLADDING APPLICATIONS

高熵合金是最近发展起来的一种新型材料，其中没有一种元素占主导地位。相反，四种或更多的元素以几乎相等的比例使用。据报道，这些合金具有广泛的吸引人的性能，包括高温下的高强度，良好的耐腐蚀性和承受辐照损伤的能力。这些特性使HEAs成为用作钠冷却快堆燃料包壳的有力候选材料。这些反应堆可以在更高的温度下运行，使用更少的燃料，而且比目前的水冷式和气冷式反应堆更安全。然而，如果高等教育机构要在这种高度竞争的环境中得到利用，就必须解决两个关键需求。首先是确定有前途的合金成分，制造它们并表征它们的机械行为。其次，需要了解导致优异的抗辐照损伤的机制。通过这项研究，我们将确定辐照反应是否普遍适用于所有HEAs，并制定策略来预测其他可能更好的系统进行研究。这笔拨款将使用离子辐照而不是中子，因为离子辐照更便宜，更快速，并且可以更快地在合金开发中进行周转。采用先进的显微技术研究辐照对合金组织的影响，采用新的显微力学测试方法研究辐照对合金力学行为的影响。重要的是，这些方法可用于测量温度超过900℃时的机械行为，因此可以在辐照和未辐照条件下研究工作温度下的机械性能。一旦确定了具有最佳抗辐照损伤性能的最有前途的合金，将对其抗液钠腐蚀性能进行研究。通过这种方法，我们将开发出一种新型合金，可用于钠冷快堆的燃料包壳。

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.