氚对金属力学性能影响的多尺度研究

Tritium is one of the main fusion fuels. Metal structures are used in production, application and deposition of tritium such as the first-wall in a fusion power reactor and the vessel in a special weapon. Tritium can influence metal mechanical properties and thereafter influence the structural reliability and safety of the metal structures during their life cycle. Taking one of the hydrogen resistant steels as an example, the general problem in basic science in development of fusion weapons and reactors is researched, i.e. the problem of the effects of tritium and decay produced helium-3 on metal mechanical properties. The cylinder samples for tension experiments are studied. Firstly, the contents of tritium and helium-3 in the samples are analytically solved. Then the samples are permeated through different time by high pressure hydrogen or tritium gases and tensional experiments of the permeated samples are carried out during which the macro tensional properties of and the internal micro defects and stresses within the samples are measured by general macro measurement methods and meso-micro neutron scattering measurement technologies, respectively. Finally, based on the macro and micro experimentally measured data, a multiscale numerical simulation method is developed which consists of the MD simulation for micro material properties, the FE simulation for meso-representative volume element and the FE simulation for macro mechanical properties of the samples and related simulations are performed. Through combination of experimental measurements and numerical simulations, the effects of tritium and helium-3 on mechanical properties of hydrogen resistant steels will be obtained and the micro defects and contents of tritium and helium-3 dependent constitutive relations will be proposed.

作为主要的聚变燃料，氚的生产、使用和储存都用到金属结构材料。氚会影响金属的力学性能，从而影响金属结构在全寿命周期的工作可靠性与安全性。本项目以抗氢钢为例，研究聚变武器装备和反应堆研制中的共性基础科学问题——氚及其衰变氦-3对金属力学性能的影响。研究对象为抗氢钢圆截面拉伸试样，内容包括试样中氚和氦-3浓度的解析求解、试样宏观力学性能和微缺陷与应力的实验测试、以及计及氚和氦-3浓度与材料微缺陷影响的多尺度数值模拟。其中实验测试包括先使试样经历不同时间的高压氢或氚浸透，再对试样进行拉伸和宏观力学性能测试，同时采用中子散射技术在线测试试样内部微缺陷和应力；数值模拟基于试样宏、微观实测数据，包括关联为一个整体的分子动力学模拟、代表性体积单元的有限元模拟、以及试样宏观力学性能的有限元模拟。通过实测和模拟的结合，获得氚和氦-3对抗氢钢力学性能的影响规律，建立计及氚和氦-3浓度与微缺陷影响的材料本构关系。

在多种工程结构中存在着临氚、临氢的金属构件，这些构件的力学性能往往是结构的安全性、可靠性方面的关键因素。本项目开展了高压氚对试样浸透和在试样中扩散的理论研究，获得试样中氚和氦-3浓度的分布及随时间的变化规律；对氚浸透试样断口进行SEM观察并对拉伸过程中的氢浸透试样进行中子散射检测，获得氚和氦-3浓度对试样断口显微组织的影响规律和试样中微缺陷的形状、尺寸与分布及其随氢浓度和拉力的变化规律；然后利用宏、微观实测数据，基于分子动力学方法等建立材料力学性质的微-细-宏观多尺度数值模拟方法，实现考虑氚和氦-3浓度与材料内部微缺陷影响的多尺度数值模拟；最后通过将多尺度数值模拟和实测结果结合，分析、认识氚和氦-3对21Cr6Ni9Mn不锈钢力学性质的影响规律，并建立计及内部氚与氦-3浓度及微缺陷影响的材料本构关系。. 依靠新发展起来的应力和缺陷的中子检测技术等实验条件，对21Cr6Ni9Mn钢试样的拉伸变形和断裂过程进行了多尺度实验观测。基于实验信息，建立了跨尺度关联的21Cr6Ni9Mn钢三尺度数值模拟模型体系并校准了其中的参数和各尺度的补充信息。进行三尺度计算，给出的具有不同内部氢浓度21Cr6Ni9Mn钢的屈服强度与实测值相差不超过10%、断面收缩率在氢浓度大于0.0004的范围内与实测值相差不超过10%。. 实验观察和数值模拟发现：氢压机理、氢促位错相互作用机理在21Cr6Ni9Mn钢的氢脆问题中不占主导，而氢吸附降低表面能和氢致晶格脆化的共同作用占主导作用；只要FCC相稳定存在，大部分氢原子就没有长距离移动的趋势；对于临氢环境中的21Cr6Ni9Mn钢构件，如果通过中子观测确定其整个实体均保持为FCC相，就可以确信其氢脆效应能够由本项目建立的数值模型体系描述。