Refractory high entropy alloys (RHEAs) have drawn growing attention due to their remarkable strength retention at high temperatures. Understanding dislocation mobility is vital for optimizing high-temperature properties and ambient temperature ductility of RHEAs. Nevertheless, fundamental questions persist regarding the variability of dislocation motion in the rugged energy landscape and the effective activation barrier for specific mechanisms, such as kink-pair nucleation and kink migration. Here we perform systematic atomistic simulations and conduct statistical analysis to obtain the effective activation barriers for the mechanisms underlying various types of dislocation motion in a typical RHEA, NbMoTaW. Moreover, a stochastic line tension model is developed to calculate the activation barrier with substantially reduced computational costs. By incorporating the effective activation barriers into the crystal plasticity model, a multiscale simulation framework for predicting the mechanical properties of RHEAs is established. The ambient temperature yield strength of NbMoTaW is well-predicted by the kink-pair nucleation mechanism of screw dislocations, while the strengthening originating from screw dislocations does not predominate at high temperatures. Our work provides a robust foundation for atomistic studies of effective dislocation behaviors in random solution solids, elucidating the intricate relationship between microscopic mechanisms and macroscopic properties.

中文翻译：

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位错介导的难熔高熵合金塑性的多尺度建模

难熔高熵合金（RHEA）因其在高温下具有显着的强度保持性而受到越来越多的关注。了解位错迁移率对于优化 RHEA 的高温性能和环境温度延展性至关重要。然而，关于崎岖能量景观中位错运动的可变性以及扭结对成核和扭结迁移等特定机制的有效激活势垒的基本问题仍然存在。在这里，我们进行系统的原子模拟并进行统计分析，以获得典型 RHEA NbMoTaW 中各种类型位错运动背后机制的有效激活势垒。此外，还开发了随机线张力模型来计算激活势垒，同时大大降低了计算成本。通过将有效的活化势垒纳入晶体塑性模型，建立了预测 RHEA 机械性能的多尺度模拟框架。 NbMoTaW 的环境温度屈服强度可以通过螺型位错的扭结对成核机制很好地预测，而源自螺型位错的强化在高温下并不占主导地位。我们的工作为随机溶液固体中有效位错行为的原子研究提供了坚实的基础，阐明了微观机制和宏观特性之间的复杂关系。