Medium- to high-entropy alloys are characterized by fluctuations in chemical composition, i.e., lattice distortion (LD) and chemical short-range ordering (CSRO). However, their roles in the melting of these alloys are still unclear. Using a combination of molecular dynamics and x-ray diffraction simulations, we investigate the effects of LD and CSRO on the melting of single crystalline CoCrNi, a medium entropy alloy (MEA). LD accelerates the melting process and reduces the melting temperature by lowering the energy barrier of the nucleation of amorphous clusters and then promoting the formation of amorphization. By contrast, CSRO divides CoCrNi MEA into CoCr clusters and Ni segregated regions, localizing LD to the CoCr regions and the boundaries between CoCr clusters and Ni regions. Such a LD localization reduces the area for the nucleation of the amorphous clusters in the ordered MEA at the start of melting, resulting in a lower free energy and, thus, a much higher melting temperature than the random MEA without CSRO. As the temperature rises in the ordered MEA, the degree of CSRO decreases slightly in the beginning and then experiences a rapid reduction in the last stage of melting.

中文翻译：

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局部化学波动在中等熵合金 CoCrNi 熔化中的作用

中高熵合金的特征在于化学成分的波动，即晶格畸变 (LD) 和化学短程排序 (CSRO)。然而，它们在这些合金熔化中的作用仍不清楚。结合分子动力学和 X 射线衍射模拟，我们研究了 LD 和 CSRO 对单晶 CoCrNi（一种中等熵合金 (MEA)）熔化的影响。LD通过降低非晶簇成核的能垒进而促进非晶化的形成来加速熔化过程并降低熔化温度。相比之下，CSRO 将 CoCrNi MEA 分为 CoCr 簇和 Ni 分离区域，将 LD 定位到 CoCr 区域以及 CoCr 簇和 Ni 区域之间的边界。这种 LD 局部化在熔化开始时减少了有序 MEA 中无定形团簇的成核面积，从而导致较低的自由能，因此与没有 CSRO 的随机 MEA 相比，熔化温度高得多。随着有序MEA中温度的升高，CSRO的程度在开始时略有下降，然后在熔化的最后阶段迅速下降。