界面对高温辐照下低活化马氏体钢强度的影响研究

Fusion reactor is one of the hot research directions for nuclear energy development in China. The relationship between microstructure and mechanical properties of reduced activation martensitic steel in high temperature and irradiation condition is the key problem for the reactor safety service and Chinese fusion reactor research and development, and the effect of high temperature and irradiation on interface is one of the key issues in current research. The effect of high temperature and irradiation on the interface is extremely complicated, influenced by many factors, as the interface defects, interface element segregation, interface precipitation and others. The quantitative relationship between most factors and interface strength is still not clear. The unclear mechanism of the effect of high temperature and irradiation on the interface bonding strength of reduced activation martensitic steel at the micro scale will also lead to the lack of theoretical analysis of the strength in the macro scale. Therefore, the unclear mechanism of the effect of high temperature and irradiation on the interface bonding strength of reduced activation martensitic steel has become an important bottleneck which restricts the further development of reduced activation martensitic steel and the deep mining of the experimental results in high temperature and irradiation conditions. This study plans to analyze various factors of interface (mainly grain boundaries and martensite lath boundaries) in reduced activation martensitic steel and the relationship of interface microstructure evolution and interface bonding strength, in order to further clarify the effect of high temperature and irradiation on the strength of reduced activation martensitic steel.

聚变堆是我国现今核能研发的热点方向之一。低活化马氏体钢在高温辐照条件下显微组织和力学性能的关系是实现反应堆安全服役、促进我国聚变堆研究发展的关键问题，而其中高温辐照对材料界面的影响是现今研究关注的重点问题之一。高温辐照作用下，界面强度变化本身就是极为复杂的问题，受界面缺陷、界面元素偏聚、界面析出等诸多因素影响，而大多数影响因素与界面结合强度的定量关系都尚不明确。在微观尺度中高温辐照对低活化钢界面结合强度影响机制的不明确又会进一步导致宏观尺度中高温辐照条件下低活化钢强度理论分析的欠缺。因此，高温辐照条件对界面结合强度的影响机制的不清晰已成为了制约高温辐照条件下低活化钢强度理论的进一步发展、限制对实验结果信息深入挖掘的重要瓶颈问题。本研究计划分析多种因素对低活化马氏体钢中界面处(主要是晶界和马氏体板条界)组织演化以及界面结合强度的综合影响，以进一步明确高温辐照影响低活化钢强度的物理本质。

聚变能作为一种高效、安全、清洁的能源越来越受到人们的重视。低活化铁素体/马氏体钢被认为是聚变堆的首选结构材料，其在高温和辐照条件下的组织演化和力学响应是制约聚变堆发展建设的关键科学问题。.低活化钢在高温辐照环境下包括晶界元素偏聚、嬗变气泡形核长大以及析出相粗化的复杂相变行为决定了其服役行为。采用He离子高温辐照实验，对辐照相变行为进行了充分表征。基于速率理论分析晶界Cr元素的偏聚规律，阐明随辐照温度升高Cr元素由空位扩散机制到填隙子扩散机制的转变是其由晶界偏聚向贫化转变的原因。利用相场建立气泡、析出相模型，引入各向异性的界面能，解释了气泡方形形貌的形成原因，引入K-S位向关系应变能，说明M23C6析出相长条状形貌的产生原因。在此基础上，利用相场模型系统研究温度、剂量、剂量率等辐照条件对低活化钢中气泡演化的影响：气泡优先在晶界和相界形核长大，辐照温度升高，点缺陷扩散速度提高，界面气泡快速进入粗化阶段，尺寸变大，密度降低，界面周围的贫化效应更显著；辐照剂量率提高，气泡演化加快，达到相同剂量时气泡尺寸更大，密度更高。.基于高温辐照相变的研究调整合金成分，在沈阳金属所、东北大学进行了5批次14炉200kg级别的低活化钢制备，迭代筛选2种改进型低活化钢，系统研究热处理制度对其性能的影响并改进热处理工艺，成功细化析出、提高析出密度，在高温时效、蠕变（超过10000小时）评价中均表现出较高的性能优势和发展潜力，已经开始中子辐照测试。.结合蠕变实验结果，基于空洞生长建立蠕变模型，通过耦合扩散和蠕变的贡献，得到了与模型合金相近的空洞体积分数，蠕变寿命预测结果与实验符合较好，为低活化钢在高温辐照服役环境下的蠕变行为预测奠定基础。.研究结果深化了人们对材料的辐照、蠕变效应的理解，对核聚变堆材料的发展具有重要意义。