The bulk and grain-boundary diffusivity of Mn in 20/25/Nb stainless steel was measured at 550 to 1250C. The bulk diffusion at 740 to 1250C could be described by:

D (cm2/s) = 2.1 x 10-1 exp[-59.2(kcal/mol)/RT]

The grain-boundary diffusion at 550 to 750C could be represented by:

D (cm3/s) = 1.1 x 10-6 exp[-46.1(kcal/mol)/RT]

An apparent enhancement of the bulk diffusion coefficient occurred below 740C, but no systematic dependence upon dislocation density was observed.

A.F.Smith: Zeitschrift für Metallkunde, 1975, 66[11], 692-5