Analytical electron microscopy was applied to interdiffusivity measurements, using Ni/Ni-8mol%Ti couples. The high spatial resolution of this method revealed that there was an effect of annealing atmosphere upon the concentration profiles and microstructures within several microns of the Kirkendall interface. Distortion of the concentration profiles, and the formation of Ti-rich particles and/or regions, were observed near to the interface. The interdiffusivities which were measured by using Sauer-Freise analysis of the concentration profiles, in the absence of an annealing atmosphere, were in good agreement with published values of the interdiffusivities and impurity diffusivities of Ti in Ni. The interdiffusivities could be described by the expressions:

2mol%Ti:     2.46 x 10-5 exp[-242(kJ/mol)/RT]

4mol%Ti:     3.08 x 10-5 exp[-243(kJ/mol)/RT]

6mol%Ti:     2.37 x 10-5 exp[-238(kJ/mol)/RT]

The values were higher, by an order of magnitude, than self-diffusivities in Ni.

Analytical Electron Microscopy Study of Ni/Ni-8mol%Ti Diffusion Couples N.Komai, M.Watanabe, Z.Horita, T.Sano, M.Nemoto: Acta Materialia, 1998, 46[12], 4443-51