Modified deformation behaviour of self-ion irradiated tungsten: A combined nano-indentation, HR-EBSD and crystal plasticity study
Modified deformation behaviour of self-ion irradiated tungsten: A combined nano-indentation, HR-EBSD and crystal plasticity study
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DOI：
10.1016/j.ijplas.2020.102817
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发表时间：
2020-12-01
影响因子：
9.8
通讯作者：
Hofmann, Felix
中科院分区：
文献类型：
--
作者：
Das, Suchandrima;Yu, Hongbing;Hofmann, Felix
预测辐照损伤引起的机械和物理性能的剧烈变化是未来核裂变和聚变反应堆设计的关键。自离子辐照为模拟中子辐照效应提供了一种有吸引力的工具。然而，自离子注入样品的损伤层只有几微米厚，难以估计其宏观性能。在这里，我们使用实验和建模技术的组合来解决这一挑战。我们专注于自离子注入钨，这是核聚变反应堆装甲组件和原型bcc材料的领先者。为了捕捉性能的剂量依赖演化，我们实验表征了样品的损伤水平从0.01到1dpa。晶粒的球形纳米压痕显示硬度增加到0.032 dpa剂量，超过该剂量就饱和了。原子力显微镜（AFM）测量显示，堆积增加到相同的剂量，超过大堆积和滑步可见。基于这些观察结果，我们建立了辐照材料的简单晶体塑性有限元模型。它捕获了辐照诱导硬化，然后通过辐照诱导缺陷和滑动位错的相互作用进行应变软化。辐照诱导缺陷的剪切阻力是基于物理的，通过对类似辐照样品的透射电子显微镜（TEM）观察来估计。模拟了0.01、0.1、0.32和1dpa剂量下原始钨和注入钨的纳米压痕。只有两个模型参数与0.01 dpa样品的实验结果拟合，并对所有其他剂量保持不变。CPFE模型预测的压痕峰值载荷、压痕表面轮廓和损伤饱和度与实验结果吻合较好。预测的晶格畸变和凹痕周围的位错分布与高分辨率电子背散射衍射（HR-EBSD）的相应测量结果吻合良好。最后，利用CPFE模型预测了类似辐照下块状钨材料的宏观应力应变响应。这些宏观信息是融合装甲部件设计所需的关键输入。
Predicting the dramatic changes in mechanical and physical properties caused by irradiation damage is key for the design of future nuclear fission and fusion reactors. Self-ion irradiation provides an attractive tool for mimicking the effects of neutron irradiation. However, the damaged layer of self-ion implanted samples is only a few microns thick, making it difficult to estimate macroscopic properties. Here we address this challenge using a combination of experimental and modelling techniques. We concentrate on self-ion-implanted tungsten, the frontrunner for fusion reactor armour components and a prototypical bcc material. To capture dose-dependent evolution of properties, we experimentally characterise samples with damage levels from 0.01 to 1 dpa. Spherical nano-indentation of grains shows hardness increasing up to a dose of 0.032 dpa, beyond which it saturates. Atomic force microscopy (AFM) measurements show pile-up increasing up to the same dose, beyond which large pile-up and slip-steps are seen. Based on these observations we develop a simple crystal plasticity finite element (CPFE) model for the irradiated material. It captures irradiation-induced hardening followed by strain-softening through the interaction of irradiation-induced-defects and gliding dislocations. The shear resistance of irradiation-induced-defects is physically-based, estimated from transmission electron microscopy (TEM) observations of similarly irradiated samples. Nano-indentation of pristine tungsten and implanted tungsten of doses 0.01, 0.1, 0.32 and 1 dpa is simulated. Only two model parameters are fitted to the experimental results of the 0.01 dpa sample and are kept unchanged for all other doses. The peak indentation load, indent surface profiles and damage saturation predicted by the CPFE model closely match our experimental observations. Predicted lattice distortions and dislocation distributions around indents agree well with corresponding measurements from high-resolution electron backscatter diffraction (HR-EBSD). Finally, the CPFE model is used to predict the macroscopic stress-strain response of similarly irradiated bulk tungsten material. This macroscopic information is the key input required for design of fusion armour components.