Effect of high magnetic field on intermetallic phase growth in Ni-Al diffusion couples

The effect of a 12T high magnetic field on the intermetallic phase growth in Ni-Al diffusion couples was studied in this paper. It was found that Ni2Al3 and NiAl3 formed in the couples prepared by the pouring technique. After annealing with or without the magnetic field, the diffusion zones were still composed of Ni2Al3 and NiAl3. The thickness of each intermetallic layer was also examined. The results demonstrate that the magnetic field reduces the thickness of Ni2Al3 and NiAl3 layers. This reduction of intermetallic layer thickness can be attributed to the decreasing frequency factor under the magnetic field. However, the activation energy for layer growth is independent of the application of the magnetic field. The magnetic field direction has an effect on the layer growth of the Ni2Al3 and NiAl3, which might result from the change of the probability of the atomic jump in the magnetic field direction. The decrease of the layer thickness suggests that the diffusion of atoms is retarded under the magnetic field. This retardation was explained based on the ambipolar diffusion theory. (C) 2008 Elsevier B.V. All rights reserved.