Study On The Diffusion Behavior Of Al/Cu And Al/Mg Binary Systems Under High Magnetic Fields

Diffusion is the main way to be transportation of substance. the microstructure and performance of material could be improved by means of effective control of the diffusion of atoms. Various metallurgical phenomenons, such as solid phase transformation, recrystallization, grain boundary migration, are closely related with the diffusion of atoms. The high magnetic fields affect on these process significantly. Therefore, the study on the diffusion under high magnetic field will make great contribution to found and complete the theory of material science in high magnetic fields; on the other hand, some metallurgical phenomena under high magnetic fields could be find answers or guides from such studies.By means of optical microscope, digital microscopy, electronic microprobe analyzer, scanning electronic microscope etc, we researched the diffusion behavior of Al-Cu liquid/solid and Al-Mg solid/solid under high magnetic field, in addition, we also examined the effecting of the diffusion at magnetic intensity and direction. In the view of kinetics, we calculated the diffusion coefficient of performance from the examination on the thickness of diffusion layer and the distance of interface migration, and in the view of thermodynamics, we also calculated the diffusion constant and diffusion activation energy under high magnetic field in this paper.We concluded that there always were three intermetallics (δ, ζ2, η2) created from Cu side to Al side regardless of the high magnetic field. With11.5T magnetic field, the thickness of diffusion layer trended to be thin obviously, and the exponential relationship between the thickness of diffusion layer and time consumed when heat treatment was totally matched. If without any magnetic field existed, the growth of Al-Cu diffusion layer was combined action both chemical reaction and volume diffusion of group component, however, under the condition of11.5T magnetic field, the volume diffusion of group component played the important role on the growth of diffusion layer. As a result, the high magnetic field could decrease the diffusion coefficient by increasing the activation energy of diffusion. Therefore, the growth of diffusion layer could be hindered effectively.The research of Al-Mg solid/solid binary metal diffusion under the high magnetic field showed that there always two intermetallics (γ, β) created at the interface of Al-Mg, after magnetic field settled down, the diffusion layer thickened and the exponential relationship between the thickness of diffusion layer and time consumed when heat treatment matched. If the diffusion direction difference from orientation of magnetic field, the thickness of diffusion layer altered obviously beneath at370℃. When temperature heated up, for example at400℃, the thickness of diffusion layer hardly altered because the thermal disturbance restricted the orientation of magnetic field. At the condition of no magnetic field existed, the growth of y layer was controlled by the grain boundary diffusion and grain growth, otherwise, the growth was controlled by the volume diffusion of group component. Whatever the magnetic field existed or not, the growth of β layer was controlled by the volume diffusion of group component. The results was that magnetic field increased the effective diffusion coefficient D by increasing diffusion constant Do, therefore promoted the growth of Al-Mg diffusion layer.