Medium- and high-entropy alloys are an emerging class of materials that can exhibit outstanding combinations of strength and ductility for engineering applications. Computational simulations have suggested the presence of short-range order (SRO) in these alloys, and recent experimental evidence is also beginning to emerge. Unfortunately, the difficulty in quantifying the SRO under different heat treatment conditions has generated much debate on the atomic preferencing and implications of SRO on mechanical properties. Here we develop an approach to measure SRO using atom probe tomography. This method balances the limitations of atom probe tomography with the threshold values of SRO to map the regimes where the required atomistic neighbourhood information is preserved and where it is not. We demonstrate the method with a case study of the CoCrNi alloy and use this to monitor SRO changes induced by heat treatments. These species-specific SRO measurements enable the generation of computational simulations of atomic neighbourhood models that are equivalent to the experiment and can contribute to the further understanding and design of medium- and high-entropy alloys and other materials systems where SRO may occur.

中熵和高熵合金是一类新兴材料，可以在工程应用中表现出出色的强度和延展性组合。计算模拟表明这些合金中存在短程有序（SRO），最近的实验证据也开始出现。不幸的是，在不同热处理条件下量化 SRO 的困难引起了关于原子偏好和 SRO 对机械性能影响的很多争论。在这里，我们开发了一种使用原子探针断层扫描测量 SRO 的方法。该方法平衡了原子探针断层扫描的局限性与 SRO 的阈值，以绘制保留和不保留所需原子邻域信息的区域。我们通过 CoCrNi 合金的案例研究演示了该方法，并用它来监测热处理引起的 SRO 变化。这些特定物种的 SRO 测量能够生成相当于实验的原子邻域模型的计算模拟，并有助于进一步理解和设计中熵和高熵合金以及可能发生 SRO 的其他材料系统。