The grain boundary diffusion of Cu in Al was investigated by means of electron probe micro-analysis at 300 to 400C. The triple product, sδDgb, was calculated via the Fisher–Gibbs solution using two methods—measurement of grain boundary concentrations as a function of penetration depth, and the contour angle (at the top of the diffusion wedge). In the first case,

sδD(m3/s) = 5.1 x 10-11exp[-102(kJ/mol)/RT]

In the second case,

sδD(m3/s) = 1.4 x 10-11exp[-94(kJ/mol)/RT].

Cu Diffusion along Al Grain Boundaries. N.Dolgopolov, A.Rodin, A.Simanov, I.Gontar: Materials Letters, 2008, 62[30], 4477-9