中文摘要：

研究了在有、无外加磁场条件下热处理时，低活化钢中析出相的长大规律及其对力学性能的影响．经高温强磁场热处理后低活化钢的屈服强度和抗拉强度均比无磁场热处理时低，而冲击韧性并无明显变化．强磁场显著抑制M23C6（M=Cr，W和Fe）沿原奥氏体晶界和马氏体板条界定向长大，强磁场下碳化物／铁素体界面能增大是导致长杆状M23C6碳化物球化的主要因素，并导致析出相颗粒密度降低，平均尺寸增大．利用Langer-Schwartz模型描述了低活化钢在高温强磁场条件下析出相的粗化过程．构建三维立体模型修正了屈服强度与沉淀强化关系的公式，定量描述了析出相的粗化过程对低活化钢力学性能的影响，模拟结果与实验结果符合较好．

英文摘要：

The long-term exposition of reduced activation steels under high temperature and high magnetic field leads to the microstruetural changes. And the microstructure evolution will damage the safety of fusion reactors. This work investigated the influence of high magnetic field on precipitation behavior and mechanical properties in reduced activation steels. As-quenched steels were tempered at 923 K for 3 h with and without a i0 T magnetic field. Tensile strength of the specimens tempered with a 10 T magnetic field decreased in comparison with the specimens tempered without magnetic field. The precipitation behaviors in reduced activation steels were also studied. The results indicated that the applied field could effectively prevent the directional growth of rod-shaped M23C6（M=Cr, W and Fe） carbides along martensite packet boundaries. The aspect ratio of M23C6 carbides decreased due to the increasing of the carbide/ferrite interfacial energy under the high nlagnetic field. Application of the Langer-Schwartz theory to model metal carbide precipitation behavior under the magnetic field was described. The results indicated that the density of precipitates decreased and its mean size increased owing to an increase of the precipitate/ferrite interracial energy. The model could predict the coarsening process of precipitates in reduced activation steels. Moreover, an improvement of the formula between yield strength and mean size of precipitates was also made.