Han Ying, Chen Hangman, Sun Yongwen, Liu Jian, Wei Shaolou, Xie Bijun, Zhang Zhiyu, Zhu Yingxin, Li Meng, Yang Judith, Chen Wen, Cao Penghui, Yang Yang
Department of Engineering Science and Mechanics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA.
Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA.
Nat Commun. 2024 Aug 1;15(1):6486. doi: 10.1038/s41467-024-49606-1.
Recent research in multi-principal element alloys (MPEAs) has increasingly focused on the role of short-range order (SRO) on material performance. However, the mechanisms of SRO formation and its precise control remain elusive, limiting the progress of SRO engineering. Here, leveraging advanced additive manufacturing techniques that produce samples with a wide range of cooling rates (up to 10K s) and an enhanced semi-quantitative electron microscopy method, we characterize SRO in three CoCrNi-based face-centered-cubic (FCC) MPEAs. Surprisingly, irrespective of the processing and thermal treatment history, all samples exhibit similar levels of SRO. Atomistic simulations reveal that during solidification, prevalent local chemical order arises in the liquid-solid interface (solidification front) even under the extreme cooling rate of 10K s. This phenomenon stems from the swift atomic diffusion in the supercooled liquid, which matches or even surpasses the rate of solidification. Therefore, SRO is an inherent characteristic of most FCC MPEAs, insensitive to variations in cooling rates and even annealing treatments typically available in experiments.
多主元合金（MPEA）的最新研究越来越关注短程有序（SRO）对材料性能的作用。然而，SRO的形成机制及其精确控制仍然难以捉摸，这限制了SRO工程的进展。在此，利用先进的增材制造技术制备具有广泛冷却速率（高达10K/s）的样品，并采用一种改进的半定量电子显微镜方法，我们对三种基于CoCrNi的面心立方（FCC）MPEA中的SRO进行了表征。令人惊讶的是，无论加工和热处理历史如何，所有样品都表现出相似水平的SRO。原子模拟表明，在凝固过程中，即使在10K/s的极端冷却速率下，液固界面（凝固前沿）也会出现普遍的局部化学有序。这种现象源于过冷液体中原子的快速扩散，其速度与凝固速度相当甚至超过凝固速度。因此，SRO是大多数FCC MPEA的固有特性，对冷却速率的变化甚至实验中通常采用的退火处理都不敏感。
