Diffusion Behavior Of Carbide Forming Elements(Cr、V、W)in Pure Iron Under Different Magnetic Field Strength

Heat-resistant steel is important structural material used for nuclear fusion,nuclear fission in energy field.Tokamak is one of the most important components of the fusion reaction,whose main function is to restrain plasma for realizing controllable fusion reaction and the release of fusion energy under high magnetic field.The service environment of low activation steel is high temperature and strong magnetic field.Therefore,the performance changes,failure and destruction of heat-resistant steel is crucial to nuclear fusion reactor.Carbide is an important phase in the heat-resistant steel,whose precipitation and evolution of have extremely important impact on high temperature creep properties of low activation steel and heat resistant steel.Diffusion is an important process for the structure and properties of steels,so the study of the diffusion of solute atoms in strong magnetic field has important effect the precipitation and evolution of carbide in heat-resistant steel.In this paper,by means of optical microscope,electronic microprobe analyzer,scanning electronic microscope etc,the solid diffusion behavior of Fe-Cr,Fe-V,and Fe-W were researched under different magnetic field strength.Boltzmann-Matano plane solution method was used to calculate the interdiffusion coefficient of the diffusion couple.The research of Fe-Cr diffusion couple under high magnetic fields showed that the diffusion coefficient of Cr in Fe decreases first and then increases with the increase of Cr concentration.The diffusion coefficient and diffusion distance of Cr in Fe are reduced under high magnetic field.The magnetic field suppresses the diffusion of Cr in Fe by reducing the frequency factor rather than the diffusion activation energy.The research of Fe-V diffusion couple under high magnetic fields showed that the magnetic field increases the thickness of the diffusion layer,and this effect increases with the increase of the magnetic field strength.The diffusion coefficient of Fe in V is not constant,but decreases with the increase of Fe concentration.The magnetic field increases the diffusion coefficient of Fe in pure V,and the diffusion coefficient increases with the increase of magnetic field.The research of Fe-W diffusion couple under high magnetic fields showed that the magnetic field suppresses the diffusion of W atoms in Fe;the magnetic field reduces the diffusion layer thickness,and the magnetic field decreases the diffusion coefficient of W in Fe.