The effect of pressure upon In diffusion along 2 grain boundaries in bicrystals was investigated. The grain boundaries were of symmetrical tilt-type, with a <001> misorientation axis. The tilt angle of one grain boundary was 36.5º, which corresponded to the near-S5 coincidence orientation. The other grain boundary was a general boundary with a tilt angle of 45º. Diffusion along the <001> tilt axis took place at 923K under pressures of up to 1GPa. Activation volumes of 0.94O for bulk diffusion, -0.5O for diffusivity on the near-S5 grain boundary and -0.6O for diffusivity on the 45º (100) grain boundary were found; where O was the atomic volume of Cu. One interpretation of the results was that the In atoms diffused along the <001> tilt axis via an interstitialcy mechanism; for which the activation volume was close to zero. Another explanation was based upon the observation that the parameter which was measured was the grain-boundary diffusivity, which depended upon the product of the grain boundary diffusion coefficient and the segregation factor. Enhancement of the In segregation by pressure would then tend to increase the grain-boundary diffusivity. It was concluded that both interpretations were possible, and the fact that the atomic volume of In was a factor of 2.2 higher than that of Cu could play an important role in increasing the segregation of In under pressure as well as in the diffusion mechanism itself.

The Effect of Pressure on Indium Diffusion along <001> Tilt Grain Boundaries in Copper Bicrystals. W.Lojkowski, U.Sodervall, S.Mayer, W.Gust: Interface Science, 1998, 6[3], l87-96