Volume and grain boundary diffusion of t13Sn in aluminium was investigated with the radiotracer method. The implantation technique was used for tracer deposition to avoid problems of tracer hold-up caused by the oxide layer always present on aluminium. The diffusion penetration was chosen large enough to permit serial sectioning of samples with the aid of a microtome.
The temperature dependence of the volume diffusivity was determined as D(T)=4.54 x 10-s x exp [-(114.5 + 1.2) kJ tool-~/R T] m2 s-2. This confirms previous measurements from our group which already showed that Sn is the fastest foreign metal diffusor so far investigated in aluminium.
Grain boundary diffusion of a t3Sn in A1 polycrystals was measured in the type-B kinetic regime. The grain boundary diffusion product P=s(~Dg b (s= segregation factor, 6=grain boundary width, Og b = grain boundary diffusivity) was found to be strongly affected by the impurity content of aluminium, For A1 polycrystals of 99.9992% nominal purity we obtained PsN(T)=l.08xl0-Sexp [--(96.9+7.5) kJ mol-~/RT] m 3 s -1 and for less pure A1 polycrystals of 99.99% nominal purity P4N(T)=3.0x 10 -~° exp [--(90.1+4.2) kJ mol-1/RT] m3s-~ was determined. The grain boundary diffusion product in the purer material is more than one order of magnitude higher than in the less pure material. Very likely this is an effect of co-segregation of non-diffusant impurities into the grain boundaries.