EFFECTS OF THE GRAIN-BOUNDARY SEGREGANTS P, S, C AND N ON THE GRAIN-BOUNDARY SELF-DIFFUSIVITY IN ALPHA-IRON

Bulk and grain boundary self-diffusivities of Fe were determined by a radiotracer method. The impurities in the starting material were scavenged with titanium, eleven different melts were prepared. **5**9Fe was electrodeposited on the specimens, diffusion anneals were conducted at temperatures in the range from 550 to 810 degree C. Depth profiles of the radioactivity were determined by measuring the residual activity after successive abrasions. In the samples doped with P and S the grain boundary concentrations of the dopants were determined by AES. The grain boundary self-diffusion is most rapid in pure iron where the activation energy is (91 plus or minus 4) kJ/mol. All dopants decrease the grain boundary transport, the corresponding activation energies are between 164 and 223 kJ/mol for all doped materials.