On the Theory of Diffusion in a Magnetic Field

Abstract

Diffusion in the weakly paramagnetic aluminum (rich) – copper system has been investigated in a magnetic field. Aluminum – aluminum/3% copper solid diffusion couples were diffusion annealed in a magnetic field of 30 and 20 kilo-oersteds, and then analyzed for diffusion using a microhardness technique. A statistically significant 25% decrease in the diffusivity was found for the couples annealed in a 30-kilo-oersted field applied perpendicular to the diffusion direction. However, from the accuracy of the results it is not possible to determine whether the field affects only the frequency factor D0, the activation energy E, or both factors. A theory based on the plasma–agnetohydrodynamic properties of the alloy system is developed to explain the results. According to the theory, the magnetic field decreases the diffusivity by the factor 1/(1 + ωce2/νe2), where ωce and νc are the cyclotron and collision frequencies respectively of the diffusion-transported electrons. The plasma-oscillation screening effect is discussed, and it is shown that the field does not significantly affect charge screening. It is thus proposed that the diffusivity is decreased through the frequency factor D0, and not through the activation energy of the atom-vacancy jump process.

Structural control of Fe-based alloys through diffusional solid/solid phase transformations in a high magnetic field

“…Among these transformations, diffusion is very important in diffusional transformations, but there have been very few studies on the effects of a magnetic field on diffusion. Youdelis et al [65] reported that a magnetic field of 3 T suppressed the diffusivity of Cu in Al perpendicular to the direction of the field by about 25%. Now ever, Nakajima et al [66] did not find any effect of a magnetic field on the diffusion of Ni in Ti.…”

Effect of a High Magnetic Field on Carbon Diffusion in γ-Iron

“…Youdelis et al 1) reported that a 3 T magnetic field retarded the diffusion of copper in aluminium. Nakajima et al 2) observed no magnetic effects on the diffusion of nickel in titanium.…”

Influence of strong static magnetic field on intermediate phase growth in Mg–Al diffusion couple

“…The influence of static magnetic field on the diffusion behavior was firstly studied by Youdelis et al [10,11], who found diffusion suppression caused by static magnetic field and later by Nakajima et al [12], who, on the contrary, did not observe such effects. A shortcoming in their study is that the magnetic * Corresponding author.…”