The tracer grain-boundary diffusion of 51Cr and 59Fe at 773 to 1273K was studied, using serial-sectioning, in material that had been modified with Fe, Cr or Zr. It was found that additions of Fe and Cr, of up to about 6at%, did not alter the activation enthalpy for Cr grain boundary diffusion, whereas alloying with Zr (up to 1.6at%) led to a significant increase in the activation enthalpy for Cr grain boundary diffusion (tables 10 and 11). The values of activation enthalpy for Fe grain boundary diffusion in the same materials were smaller than the activation enthalpies for Cr grain boundary diffusion, and they increased slightly with increasing concentration of Fe or Cr. A decrease in activation enthalpy for Fe grain boundary diffusion, with increasing Zr concentration, was observed in Zr-doped alloys. The results were explained in terms of an atomic-size effect and the differing affinities between Zr and Cr and between Zr and Fe atoms.

Short-Circuit Diffusion of 51Cr and 59Fe in Nickel-Aluminum Intermetallics. Cermák, J., Stloukal, I., Růžičková, J., Pokorná, A.: Materials Science Forum, 1999, 294-296, 569-72

Figure 9

Estimated tracer diffusion coefficients of Cr, Fe, Nb and Ti in Ni3Al

Table 10

Arrhenius parameters for 51Cr grain boundary diffusion in Ni3Al

Table 11

Arrhenius parameters for 59Fe grain boundary diffusion in Ni3Al