Tracer diffusion of Cr in Ni and Ni-22Cr studied by SIMS

The volume diffusion of Cr in Ni and in Ni-22Cr (at. %) was studied from tracer experiments, using Cr-52 and Cr-54 as tracers, in the temperature range 542-843 degrees C. Intensity-depth profiles were generated by secondary ion mass spectrometry (SIMS), which allowed data to be obtained at substantially lower temperatures than previously available. Chromium diffusion was found to be slightly slower in Ni-22Cr than in Ni, in agreement with literature data at high temperature. The mobility parameters (ln(D-0)(Cr)Ni = -1.6 +/- 0.3 [cm(2)/s], Q(Cr)(Ni) = 260 +/- 2 kJ/mol for Cr in Ni, and ln(D-0)(Cr)(Ni-22Cr) = -0.3 +/- 1.3 [cm(2)/s], Q(Cr)(Ni-22Cr) = 279 +/- 10 kJ/mol for Cr in Ni-22Cr) are in the lower range of those obtained by previous investigators in similar alloys. The present results indicate that the vacancy-solute exchange mechanism in effect at high temperature does not change significantly at least down to 542 degrees C.