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 (63)Ni radioisotope in combination with the radiotracer serial sectioning technique was applied at higher temperatures and the secondary ion mass spectrometry ((64)Ni 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 Ni(50-x)Fe(x)Al(50) 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 Ni(40)Fe(10)Al(50) composition and a conspicuous maximum around the Ni(25)Fe(25)Al(50) composition. (c) 2005 Elsevier Ltd. All rights reserved.