EFFECT OF HIGH MAGNETIC FIELD ON PRECIPITATION BEHAVIORS AND MECHANICAL PROPERTIES IN REDUCED ACTIVATION STEELS

Abstract

The long-term exposition of reduced activation steels under high temperature and high magnetic field leads to the microstructural 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 10 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 magnetic 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 interfacial 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.