Influence of microstructure on the diffusivity of hydrogen in advanced steels

众所周知，金属系统中氢的大量积累会促进过早失效，这是当前和未来核反应堆的主要问题。在高级钢中，由于其复杂的微观结构，非常高的强度和H在钢中的低溶解度，会发生这种情况。在加工过程中非常小心地防止氢的吸收，并采用高度保守和昂贵的脱气热处理方法。了解氢是如何被吸收、运输和困在钢铁内部的，可以大大提高生产这些材料的能源成本，同时又不损害它们的结构完整性。本项目旨在开展基础研究，了解和预测多相钢中微观组织对H迁移率的影响。这项工作将包括开发微结构敏感的计算模型，描述具有不同局部H扩散和捕获行为的多相合金中H的三维输运。它还旨在将这项研究与氢致脆的工作联系起来。计算工作将使用不同的实验技术进行验证，包括：(1)热解吸光谱研究不同微观结构下氢释放的变化。(2)扫描电子显微镜-包括连续切片-成像微观结构中影响H输运的关键二维和三维特征，如形态和尺寸。(3)透射电镜研究影响H扩散的纳米尺度特征和可能的力学性能损失。

Significant accumulation of Hydrogen in metallic systems is known to promote premature failure and is a primary concern in current and future nuclear reactors. In advanced steels, this happens due to their complicated microstructure, their very high strength, and the low solubility of H in steel. Extreme care is taken to prevent hydrogen absorption during processing and highly conservative and expensive approaches to degassing heat treatments are applied. Understanding how the hydrogen is absorbed, transported and trapped inside steel can yield huge improvements to the energy cost of producing these materials without compromising their structural integrity.This project is aimed at conducting fundamental studies to understand and predict the influence of the microstructure on the mobility of H in multi-phase steels. The work will involve developing microstructure-sensitive computational models describing the 3-D transport of H in alloys with multiple phases, all with different local H diffusion and trapping behaviour. It is also aimed to link this research with work on Hydrogen-induced embrittlement. The computational work will be validated using different experimental techniques including: (1) Thermal desorption spectroscopy to study the variations in H release with different microstructures. (2) Scanning Electron Microscopy - including serial sectioning - to image critical 2D and 3D features in the microstructure affecting H transport, such as morphology and size. (3) Transmission Electron Microscopy to study nano-scale features affecting H diffusion and possible loss in mechanical properties.