Yin Sheng, Zuo Yunxing, Abu-Odeh Anas, Zheng Hui, Li Xiang-Guo, Ding Jun, Ong Shyue Ping, Asta Mark, Ritchie Robert O
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
Nat Commun. 2021 Aug 11;12(1):4873. doi: 10.1038/s41467-021-25134-0.
Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation. However, they can also display a significant energetic driving force for chemical short-range ordering (SRO). Here, we investigate mechanisms underlying the mobilities of screw and edge dislocations in the body-centered cubic MoNbTaW RHEA over a wide temperature range using extensive molecular dynamics simulations based on a highly-accurate machine-learning interatomic potential. Further, we specifically evaluate how these mechanisms are affected by the presence of SRO. The mobility of edge dislocations is found to be enhanced by the presence of SRO, whereas the rate of double-kink nucleation in the motion of screw dislocations is reduced, although this influence of SRO appears to be attenuated at increasing temperature. Independent of the presence of SRO, a cross-slip locking mechanism is observed for the motion of screws, which provides for extra strengthening for refractory high-entropy alloy system.
难熔高熵合金（RHEAs）旨在具备高温强度，其中刃型位错和螺型位错在塑性变形中都起着重要作用。然而，它们也可能表现出显著的化学短程有序（SRO）能量驱动力。在此，我们基于高精度机器学习原子间势，通过广泛的分子动力学模拟，研究了体心立方MoNbTaW难熔高熵合金在宽温度范围内螺型位错和刃型位错迁移的潜在机制。此外，我们特别评估了这些机制如何受到短程有序的影响。发现短程有序的存在增强了刃型位错的迁移率，而螺型位错运动中的双扭结形核速率降低，尽管短程有序的这种影响在温度升高时似乎会减弱。与短程有序的存在无关，在螺型位错运动中观察到一种交滑移锁定机制，这为难熔高熵合金系统提供了额外的强化作用。
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