Powders of supersaturated solid solutions, with a nanocrystalline structure, were prepared by mechanical alloying. The powder was compacted into a columnar form, at low temperatures, by applying a pressure of 3GPa. The diffusion of Cu in the compacted nanocrystalline material was studied by means of ion mass microanalysis. The results could be described by:

D(m2/s) = 2.4 x 10-12exp[-34.8(kJ/mol)/RT]

It was noted that the interfacial diffusion coefficient of Cu in the nanocrystalline materials was higher than the volume diffusion coefficient of Cu in Al. The activation energy for interfacial diffusion was quite small when compared with that for the volume diffusion of Cu in Al. The characteristics of the interfacial diffusion implied that the interfaces in the present nanocrystalline materials had a very loose structure.

Y.Minamino, S.Saji, K.Hirao, K.Ogawa, H.Araki, Y.Miyamoto, T.Yamane: Materials Transactions, 1996, 37[2], 130-7

Table 64

Interdiffusion Coefficients in Al-Zn-Mg-Cu Alloys