Ni radiotracer diffusion in B2 ordered NiFeAl alloys

Ni bulk diffusion was measured in the B2 ordered NiFeAl alloys with a constant Al content of approximately 50 at.%. The 63Ni radioisotope in combination with the radiotracer serial sectioning technique was applied at higher temperatures and the secondary ion mass spectrometry (64Ni isotope) was used in a low temperature range. Arrhenius-type temperature dependencies were established for all studied compositions in the temperature interval from 1050 to 1500 K. As the Fe content x in the Ni50−xFexAl50 ternary alloys increases, the Ni diffusivity generally increases along the quasi-binary section between stoichiometric NiAl and FeAl. The activation enthalpy Q of Ni diffusion changes strongly non-monotonically in the ternary alloys between the binary end-members NiAl and FeAl revealing a pronounced minimum at the Ni40Fe10Al50 composition and a conspicuous maximum around the Ni25Fe25Al50 composition.