氚及其衰变氦-3对低活化铁素体/马氏体钢微结构损伤机理研究

Reduced activation ferritic/martensitic (RAFM) steels are considered as primary candidate structure materials in fusion reactor. During the extract tritium form tritium breeding blanket, microstructure damage of RAFM will be caused by high temperature tritium and induces material embrittlement. In this project, China low activation martensitic (CLAM) steel will be focused on microstructure damage caused by tritium and helium-3. Effects of tritium and helium-3 on lattice distortion and new defect production around vacancies and grain boundaries will be calculated through first principles, and corresponding simulation model of microstructure damage will be obtained. Positron annihilation technology will be used to detect the types and size of vacancy defects in CLAM steels after tritium charging and aging. Electron microscopy will be performed to observe grain boundary orientation distribution and effects of aggregation of tritium and helium-3 on stacking fault and corrosion cracking around grain boundaries. Combining theoretical simulation and experimental measurement, mechanism of tritium and helium-3 on microstructure damage in CLAM steel will be explored. This project will provide fundamental knowledge for changes of mechanical properties in structure materials due to microstructure damage, and is scientific to optimize design of materials resistant to hydrogen and helium damage。

低活化铁素体/马氏体（RAFM）钢是聚变堆的首选结构材料，在聚变堆氚增殖剂包层产氚提取过程中，RAFM钢一直处于高温充氚状态，进入RAFM钢中的氚及其衰变的氦-3会导致材料的结构损伤，引起材料的脆化效应。本项目以中国低活化马氏体（CLAM）钢为研究对象，从微观动力学角度分析氚和氦-3对材料的微结构损伤。在理论计算上利用第一性原理研究氚和氦-3对RAFM钢中空位、晶界附近晶格畸变、新缺陷形成的影响，获得低活化钢微结构氚、氦-3损伤的理论模型。在实验上利用正电子湮没技术分析充氚并时效的CLAM钢样品中空位型缺陷种类、大小的变化。利用电镜分析样品的晶界取向分布以及氚和氦-3的聚集行为对晶界周围层错和腐蚀裂纹的影响。理论模拟结合实验测量，探索氚和氦-3对CLAM钢微结构损伤的机理。为RAFM钢微结构损伤导致材料力学性能变化提供基础性认识，为材料抗氢氦损伤特性的优化设计提供科学依据。

低活化铁素体/马氏体（RAFM）钢是聚变堆的首选结构材料，在聚变堆氚增殖剂包层产氚提取过程中，RAFM钢一直处于高温充氚状态，进入RAFM钢中的氚及其衰变的氦-3会导致材料的微结构损伤，引起材料的脆化效应。本项目以中国低活化马氏体（CLAM）钢为研究对象，从微观动力学角度分析氚和氦-3对材料的微结构损伤。主要结果如下：1）第一性原理计算发现He比H原子更容易导致空位附近的局域晶格膨胀，同时发现H和He原子在RAFM钢典型晶界3和5处析出能要比在体态时低；2）利用正电子湮没谱学测量了不同温度下退火的CLAM钢的正电子湮没寿命和多普勒展宽参数，发现在200℃-500℃的退火温度范围，CLAM钢中的单空位和双空位明显回复，当温度大于500℃，空位型缺陷基本完全回复。3）气态热充氢的拉伸实验发现300℃-500℃充氘后的CLAM钢的断面收缩率相较于未充氘样品减少了18%，且拉伸断口表现出明显的脆性断裂韧窝。4）对CLAM钢进行了服役温度下的气态热充氢渗透实验，获得了氢气在CLAM钢中的渗透率、扩散率和溶解度等输运参数。本项研究提供了氚及其衰变的氦-3导致的RAFM钢微结构损伤基础数据。