The effects of potassium (K) doping on the incipient plasticity of tungsten (W) under nanoindentation were investigated using a combination of experiments and mesoscale defects dynamic simulations. The transmission electron microscopy study reveal that nanometer-sized bubbles were formed through the vaporization of K in specimens prepared by spark plasma sintering. In order to investigate the mechanical properties of the K-doped W specimens, nano-characterization experiments and defect dynamics simulations were conducted, comparing with those in pure W. Nanoindentation tests reveal that the maximum shear yield stress approaches the theoretical strength in annealed pure W, while K-doped W samples exhibit significant yield drop accompanied with stochastic variations. A newly developed mesoscale defect dynamics model to concurrently couple dislocation dynamics with finite element method has been also employed to investigate micro-mechanisms of plasticity under nanoindentation and the effects of K-bubbles on the plastic deformation. The simulations revealed that the localized stress concentration induced by the K-bubbles promoted dislocation nucleation and enhanced plastic deformation, thereby reducing the yield stress, showing good agreement with the experiment.

中文翻译：

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纳米压痕下钾掺杂钨的初始塑性：实验与缺陷动力学模拟的比较


采用实验和介尺度缺陷动力学模拟相结合的方法，研究了钾 （K） 掺杂对纳米压痕下钨 （W） 初塑性的影响。透射电子显微镜研究表明，通过放电等离子体烧结制备的样品中 K 的汽化形成了纳米级气泡。为了研究 K 掺杂 W 样品的力学性能，进行了纳米表征实验和缺陷动力学模拟，并与纯 W 进行了比较。纳米压痕测试表明，退火纯 W 样品的最大剪切屈服应力接近理论强度，而 K 掺杂 W 样品表现出显着的屈服下降并伴有随机变化。新开发的中尺度缺陷动力学模型将位错动力学与有限元方法同时耦合，用于研究纳米压痕下塑性的微观机制以及 K 气泡对塑性变形的影响。模拟结果表明，K 气泡诱导的局部应力集中促进了位错成核并增强了塑性变形，从而降低了屈服应力，与实验具有良好的一致性。